Taunt and Safeguard are allowed. Pro-concept moves that allow Mega Gyarados to set up easier and don't interfere with our counters, not much to talk about here.
Thunder Wave is allowed, we already allowed Thunder and Discharge, so it's pretty obvious that we don't mind the CAP having a way of inflicting paralysis.
Toxic Spikes, Spikes, and Sticky Web are disallowed. Sticky Web is too impact-full of a move that will derail us from our goal and will potentially turn the CAP into a dedicated user of Sticky Web, that doesn't care about putting the opponent into a lose-lose scenario if the opponent chooses to KO it. Toxic Spikes and Spikes have the danger of messing with our checks and counters, are largely irrelevant in OU, and also have a danger of derailing us from our goal.
Healing Wish and Memento are disallowed because the concept is to force the opponent into a lose / lose situation, not make the perfect teammate for Mega Gyarados. Mega Gyarados is being used as a way to keep the CAP alive, and a Mega Gyarados sweep is not the end goal of our concept. Healing Wish and Memento don't leave any choice at all to the opponent, they just give to Mega Gyarados a (extra) chance to set up and sweep.
Will-O-Wisp is disallowed because it fucks up the CAP's checks and counters.
All boosting moves that raise SpA and Defense are disallowed because they all interfere with our checks and counters list. Set up moves such as Swords Dance, Dragon Dance, and Agility still need some discussion though.
Also, i included some more required moves that all or almost all fully evolved Pokemon have thanks to
srk1214, which are: Substitute, Protect, Attract, Swagger, Confide, and Double Team.
I still want more discussion about Stealth Rock, Defog, and Rapid Spin, especially the latter two. Those are some of the best support moves in OU, and giving them to an already very potent CAP is no small deal. We should see past the obvious ''all of those moves help Mega Gyarados'', and try to imagine how the CAP with those moves would fit in OU, and what its impact would be. For example, does the CAP beat the majority of the common SR users? If yes is the answer to this question, then it might not be a good idea to give to the CAP Defog or Rapid Spin, because then the CAP would be a great attacker, a great check and pivot to many Pokemon, and an excellent supporter, which could end up being too much for OU to handle, or too centralizing. To give you an example, Latias has a similar blend of power, bulk, useful typing, and supportive abilities, but is easier to wall, easier to get rid of (Pursuit weak), and has an arguably worse defensive typing. Of course it has Recover, better Speed, and different resistances, but you get the issue i am trying to highlight (i hope).
Stealth Rock is a smaller issue because its distribution is much wider, so competition between SR setters is much bigger, but we should still examine how the CAP fares against the common Defog and Rapid Spin users, to see if it would be a great SR setter or not, which combined with its other traits, could potentially make the CAP broken.
So, here are a few important question for you guys to answer:
- Does the CAP beat the majority of the common Stealth Rock users?
- Does the CAP have great synergy with most Stealth Rock weak Pokemon?
- Does the CAP beat the majority of the common Defog and Rapid Spin users?
If yes is the answer to any of the first two questions, then you might have to think again before suggesting to allow Defog / Rapid Spin, or explain why the CAP would be manageable even with those moves. Similarly, if the answer to the third question is yes, you should do the same about Stealth Rock.