Defog/Rapid Spin:
I don't think CAP 19 will be broken with either of these moves. I do worry, however, that giving CAP 19 either of these moves will promote it being used in teams simply for hazard control, rather than in a role that fits more directly with the concept. In the Concept Assessment, it was pointed out that it's almost always a bad thing to lose a Pokemon, even if the free switch grabs significant momentum for you. If CAP 19 gets the capacity to remove hazards, I worry that there's a decent chance that people will just forgo the concept and use it as a specially offensive nuke that can remove hazards. I'm not passionately against giving CAP 19 either of these moves, I just don't think it's the best direction to head. Disallow.
Stealth Rock:
I don't think SR is as big a distraction as Defog and Rapid Spin. Because there is already such a diverse pool of SR setting Pokemon, CAP 19 is going to face some pretty stiff competition, not to mention the fact that we're probably going to end up with 4MSS (between STAB, HP Fire/Ice, Taunt/Haze/Clear Smog and secondary STAB or additional coverage, most teams aren't going to want one of CAP 19's moveslots going to SR when there are so many other Pokemon that could be doing it). CAP 19 certainly doesn't need SR to fulfill the concept, but it's not going to break the concept if it gets it; I'm ambivalent on this one, but would lean towards Allow.
Encore:
Unlike Taunt or Haze/Clear Smog, I find Encore to be rather counter concept. If we were making a perfect mate for Gyarados, I would absolutely support including Encore in the movepool, since Encoring the right move could allow Gyarados a free switch that it can then begin boosting on. However, as has been stated a million times throughout the process, that's not what we're doing. Gyarados is only significant because it facilitates our concept of making the opponent not want to KO CAP 19. Generally, we shouldn't be building CAP 19 with the intention for it to switch into Gyarados to allow Gyarados to start boosting; if CAP 19 is going to let Gyarados set up, it should generally be coming off the back of a KO. Encore almost always promotes CAP 19 switching out afterwards; we're not going to be boosting, and I don't think we should be removing hazards, so once CAP 19 uses Encore, it gets out and tries to let something else take advantage of the Encore turns. This isn't a role that fits with the concept, as far as I'm concerned. Disallow.
Destiny Bond:
This one has already been discussed - in theory, it fits the concept, but it goes against the way we've implemented the concept. Destiny Bond forces a blind double switch; we're trying to get CAP 19 KO'd be a predictable set of threats that can then be taken advantage of. Disallow.
Whirlpool/Infestation:
Similar problems to Encore here. This doesn't present your opponent with a balanced choice of whether to KO CAP 19 or not. If CAP 19 traps something that it counters, well, that's just helping make CAP 19 even more powerful, which it doesn't really need. If CAP 19 traps something that counters it, either CAP 19 switches out to something that can take advantage of the free turn, or the opponent is forced to KO (unless it is able to stall the turns, and CAP 19 is powerful enough that many of its threats can be broken if they're trying to stall turns). The free turn isn't something we want CAP 19 providing too often, otherwise the concept will end up forgotten. As for forcing the opponent to KO or be KO'd, well, yes, that is technically pro-concept, but it skews the risk reward balance horribly in the favour of CAP 19's user. Again, I'll contrast with Taunt. Taunt is awesome because it hands the opponent a choice; KO CAP 19 and be setup on, or switch out and concede momentum while possibly taking a powerful attack on the switch-in. Neither or those are good, but a reasonable risk/reward assessment can be made. Handing the opponent a choice of KO or be KO'd is unreasonably in favour of CAP 19; Disallow.
Attack/Special Defense/Speed Boosting Moves:
Couldn't care less about Attack boosting moves; they're not making their way onto anything but the most gimmicky of sets competitively, so if movepool submitters want to include them for flavour, there's no competitive reason to stop them. Special Defense and Speed are bigger problems. Several Pokemon that are supposed to beat us attack from the Special side of the spectrum; with a boost or two under our belt, we end up beating them, rather than having them beat us and allow Gyarados to come in and sweep. Speed has a similar problem, allowing us to KO some frail checks that rely on outspeeding to stop us. Allow Attack boosting moves; Disallow Special Defense/Speed boosting moves.
Tailwind/Trick Room:
Either way, these moves mess with our checks/counters list. They let us outspeed things we shouldn't be outspeeding. Gyarados is already going to be boosting Speed, so it doesn't really need Tailwind; Trick Room is just awful for it because it gets slower as it boosts. Disallow both.
Haze/Clear Smog:
These moves fit well with our intent for the checks/counters list - they don't let us beat anything that we shouldn't, but they do prevent us from being setup bait. Generally, Taunt will probably be the preferred option for handling Pokemon that want to setup, but there's no problem with having these as options as well. Allow.
Perish Song:
Definitely should not be Allowed alongside Whirlpool/Infestation. That being said, I'm against the inclusion of Whirlpool/Infestation. Even so, I'm not keen on Perish Song. It does nothing to discourage KO'ing CAP 19 (actually, in very niche situations, it could create the situation that caused Aftermath to be a concern in the Ability discussion, with a KO on the final turn of Perish Song to both take down CAP 19 and deny Gyarados the chance to setup), and just forces the opponent to switch out most of the time. We have better ways to handle opposing Pokemon that are trying to setup anyway, so Perish Song isn't required for that purpose. Disallow.
Phazing Moves:
Similarly to Defog and Rapid Spin, I don't feel strongly against the inclusion of these moves. However, I feel as though including them is counter productive. Our goal is to attract a particular set of Pokemon to come in on CAP 19. Phazing moves force a random opponent onto the field, totally throwing that goal out the window. We should have either Taunt or Haze/Clear Smog to handle boosting Pokemon, so we don't need to phaze to stop that. Again, I'm not going to fight strongly against these, but I lean towards Disallow.
I don't think CAP 19 will be broken with either of these moves. I do worry, however, that giving CAP 19 either of these moves will promote it being used in teams simply for hazard control, rather than in a role that fits more directly with the concept. In the Concept Assessment, it was pointed out that it's almost always a bad thing to lose a Pokemon, even if the free switch grabs significant momentum for you. If CAP 19 gets the capacity to remove hazards, I worry that there's a decent chance that people will just forgo the concept and use it as a specially offensive nuke that can remove hazards. I'm not passionately against giving CAP 19 either of these moves, I just don't think it's the best direction to head. Disallow.
Stealth Rock:
I don't think SR is as big a distraction as Defog and Rapid Spin. Because there is already such a diverse pool of SR setting Pokemon, CAP 19 is going to face some pretty stiff competition, not to mention the fact that we're probably going to end up with 4MSS (between STAB, HP Fire/Ice, Taunt/Haze/Clear Smog and secondary STAB or additional coverage, most teams aren't going to want one of CAP 19's moveslots going to SR when there are so many other Pokemon that could be doing it). CAP 19 certainly doesn't need SR to fulfill the concept, but it's not going to break the concept if it gets it; I'm ambivalent on this one, but would lean towards Allow.
Encore:
Unlike Taunt or Haze/Clear Smog, I find Encore to be rather counter concept. If we were making a perfect mate for Gyarados, I would absolutely support including Encore in the movepool, since Encoring the right move could allow Gyarados a free switch that it can then begin boosting on. However, as has been stated a million times throughout the process, that's not what we're doing. Gyarados is only significant because it facilitates our concept of making the opponent not want to KO CAP 19. Generally, we shouldn't be building CAP 19 with the intention for it to switch into Gyarados to allow Gyarados to start boosting; if CAP 19 is going to let Gyarados set up, it should generally be coming off the back of a KO. Encore almost always promotes CAP 19 switching out afterwards; we're not going to be boosting, and I don't think we should be removing hazards, so once CAP 19 uses Encore, it gets out and tries to let something else take advantage of the Encore turns. This isn't a role that fits with the concept, as far as I'm concerned. Disallow.
Destiny Bond:
This one has already been discussed - in theory, it fits the concept, but it goes against the way we've implemented the concept. Destiny Bond forces a blind double switch; we're trying to get CAP 19 KO'd be a predictable set of threats that can then be taken advantage of. Disallow.
Whirlpool/Infestation:
Similar problems to Encore here. This doesn't present your opponent with a balanced choice of whether to KO CAP 19 or not. If CAP 19 traps something that it counters, well, that's just helping make CAP 19 even more powerful, which it doesn't really need. If CAP 19 traps something that counters it, either CAP 19 switches out to something that can take advantage of the free turn, or the opponent is forced to KO (unless it is able to stall the turns, and CAP 19 is powerful enough that many of its threats can be broken if they're trying to stall turns). The free turn isn't something we want CAP 19 providing too often, otherwise the concept will end up forgotten. As for forcing the opponent to KO or be KO'd, well, yes, that is technically pro-concept, but it skews the risk reward balance horribly in the favour of CAP 19's user. Again, I'll contrast with Taunt. Taunt is awesome because it hands the opponent a choice; KO CAP 19 and be setup on, or switch out and concede momentum while possibly taking a powerful attack on the switch-in. Neither or those are good, but a reasonable risk/reward assessment can be made. Handing the opponent a choice of KO or be KO'd is unreasonably in favour of CAP 19; Disallow.
Attack/Special Defense/Speed Boosting Moves:
Couldn't care less about Attack boosting moves; they're not making their way onto anything but the most gimmicky of sets competitively, so if movepool submitters want to include them for flavour, there's no competitive reason to stop them. Special Defense and Speed are bigger problems. Several Pokemon that are supposed to beat us attack from the Special side of the spectrum; with a boost or two under our belt, we end up beating them, rather than having them beat us and allow Gyarados to come in and sweep. Speed has a similar problem, allowing us to KO some frail checks that rely on outspeeding to stop us. Allow Attack boosting moves; Disallow Special Defense/Speed boosting moves.
Tailwind/Trick Room:
Either way, these moves mess with our checks/counters list. They let us outspeed things we shouldn't be outspeeding. Gyarados is already going to be boosting Speed, so it doesn't really need Tailwind; Trick Room is just awful for it because it gets slower as it boosts. Disallow both.
Haze/Clear Smog:
These moves fit well with our intent for the checks/counters list - they don't let us beat anything that we shouldn't, but they do prevent us from being setup bait. Generally, Taunt will probably be the preferred option for handling Pokemon that want to setup, but there's no problem with having these as options as well. Allow.
Perish Song:
Definitely should not be Allowed alongside Whirlpool/Infestation. That being said, I'm against the inclusion of Whirlpool/Infestation. Even so, I'm not keen on Perish Song. It does nothing to discourage KO'ing CAP 19 (actually, in very niche situations, it could create the situation that caused Aftermath to be a concern in the Ability discussion, with a KO on the final turn of Perish Song to both take down CAP 19 and deny Gyarados the chance to setup), and just forces the opponent to switch out most of the time. We have better ways to handle opposing Pokemon that are trying to setup anyway, so Perish Song isn't required for that purpose. Disallow.
Phazing Moves:
Similarly to Defog and Rapid Spin, I don't feel strongly against the inclusion of these moves. However, I feel as though including them is counter productive. Our goal is to attract a particular set of Pokemon to come in on CAP 19. Phazing moves force a random opponent onto the field, totally throwing that goal out the window. We should have either Taunt or Haze/Clear Smog to handle boosting Pokemon, so we don't need to phaze to stop that. Again, I'm not going to fight strongly against these, but I lean towards Disallow.