Kinda late, but i felt the need to address this. Personally, i feel that Regenerator would easily be the best ability for Metagross, although the less realistic one for it to have. With Regenerator, Metagross could become one of the best offensive and defensive pivots ever, as well as one of the best Steel-types around. When you think of Metagross's faults as a defensive and tankish Pokemon, lack of reliable recovery is probably the first thing that comes to mind, leaving Metagross very easy to wear down and usually unable to check more than 1 Pokemon. Let's take a look at some popular Pokemon that Metagross counters and then some Pokemon that it checks very well (assuming a set of 252 HP / 252 Def+ and a moveset of Meteor Mash / Bullet Punch / Ice Punch / Earthquake). It counters SubDisable Gengar, non-HP Fire Latias, Alakazam, Tyranitar, Cloyster, non-Earth Power Kyurem-B, non-CB Terrakion, Jirachi, OTR Reuniclus, Lucario, Toxicroak. All those are threatening offensive Pokemon that usually give troubles to many kind of teams. As for what Metagross checks the list will be huge so i will list the most important of them: every Outraging Dragon, Lati@s, Celebi, Hydreigon, Breloom (after Sleep Clause has been activated) being the most significant. Now just imagine if Metagross could take repeated punishment from all those Pokemon, in addition to having excellent offensive presence, resistance to SR, immunity to Toxic, Toxic Spikes, and sand, Pursuit, Bullet Punch, and Stealth Rock.
Btw i though of some other ways to make Moltres more viable, but instead of making it more balanced like some other abilities suggestions have tried (Magic Guard, Regenerator) the abilities i will propose would make Moltres even more of a double-edged sword that destroys when SR is off the field but often becomes a liability when it is up. Here we go:
What if Moltres got Sheer Force?
Not only would Moltres gain a 19% power boost (1.69 = LO * Sheer Force, 1.5 = Specs) it would also gain the ability to switch moves, use Roost, and become a lethal late game sweeper all with one simple set of Hurricane, Fire Blast, Roost, Agility. This is what i really like about Sheer Force. It makes coverage moves almost unnecessary (except from Tyranitar obviously), and so frees up slots for Moltres to use both Roost and Agility, and thus becoming an interesting and potent mix of wallbreaker, offensive tank, and late game sweeper. I am really tempted to post some calcs but i always do this and i guess it is kind of pointless, so just let me tell you this: Fire Blast in rain OHKOes max HP Jirachi 56.5% of the time after SR. So, do you think that Sheer Force would allow Moltres to compete with monstrous powerhouses of OU such as Terrakion, Landorus, and Keldeo, or it would just make it a viable OU choice.
Now on to the second ability...
What if Moltres got Adaptability?
This ability is all about power and would ensure that you would never want to give a free switch-in to Moltres. Here are some calcs for your entertainment:
- 252+ SpA Choice Specs Adaptability Moltres Hurricane vs. 248 HP / 232+ SpD Rotom-W: 147-173 (48.51 - 57.09%) -- guaranteed 2HKO after Stealth Rock
- 252+ SpA Choice Specs Adaptability Moltres Hurricane vs. 248 HP / 252+ SpD Heatran: 145-171 (37.66 - 44.41%) -- guaranteed 3HKO
- 252+ SpA Choice Specs Adaptability Moltres Hurricane vs. 248 HP / 0 SpD Jellicent: 402-474 (99.75 - 117.61%) -- 93.75% chance to OHKO
- 252+ SpA Choice Specs Adaptability Moltres Hurricane vs. 252 HP / 0 SpD Eviolite Chansey: 268-316 (38.06 - 44.88%) -- 6.64% chance to 2HKO after Stealth Rock
- 252+ SpA Choice Specs Adaptability Moltres Hurricane vs. 0 HP / 0 SpD Thundurus-T: 252-297 (84.28 - 99.33%) -- guaranteed OHKO after Stealth Rock
- 252+ SpA Choice Specs Adaptability Moltres Hurricane vs. 252 HP / 0 SpD Latias: 334-394 (91.75 - 108.24%) -- guaranteed OHKO after Stealth Rock
- 252+ SpA Choice Specs Adaptability Moltres Fire Blast vs. 4 HP / 252+ SpD Blissey in sun: 366-432 (56.13 - 66.25%) -- guaranteed 2HKO
While this ability would certainly make Moltres one of the hardest Pokemon to switch into in OU, be it in sun or in rain, it wouldn't prevent LO recoil and make Moltres even more prone to passive damage and priority (where with Sheer Force Moltres could sweep even with SR up as long as it is able to take one weak resisted hit + priority). So, which ability you think would make Moltres more viable in OU and why?