I agree on Sub PuP; I would much rather just run 4 attacks or 3 attacks.
Also, I know this is last minute and we talked about this before, but I'd like to endorse a Grass Knot slash. It allows Mega Metagross to beat the likes of Mega/normal Slowbro, Hippowdon, Quagsire, and Mega Swampert (rain is really annoying and Mega Swampert likes to attempt a MEvo against Mega Metagross). This is useful because it limits the amount of Pokemon that can serve as counters to Mega Metagross even further, meaning it is much more effective at breaking down more defensively oriented builds. I don't really like the way the third slot is currently set up; I don't think that Ice Punch is very good because Meteor Mash already does so much to Landorus-T so you can just wear into range fairly easily, while Bullet Punch only has situational utility (though these situations come up often enough that it can be a lifesaver). Other people like Ice Punch though so I'm not entirely opposed to it being on the main set, but I think that Grass Knot should be slashed as well. You don't actually need -Def/SpD nature for it to do the damage that it needs to so don't worry about that.
Would also like to see an Adamant slash for that set as well. If you've ever used it or ran some calcs you'll notice that the power difference is enormous. Thunder Punch 2HKOes SpD normal Slowbro and fully defensive normal Slowbro after SR, for example. You gain an assured 2HKO on Mega Sableye, a significant bit more damage on Landorus-T, a 2HKO on standard fast Gliscor after SR, a 2HKO on offensive SD Mega Scizor after SR, a chance to OHKO fast Azumarill (standard) after SR, a decent chance to 2HKO Rotom-W without SR, and a general damage increase against just about everything. It's obviously only for teams that don't particularly struggle with the likes of Keldeo, but in cases where you can afford the drop in Speed, it is well worth running Adamant. This also lets you run spreads with a little bit of bulk. If you need to outspeed the 100s range then you can run 303 (188 EVs), which outspeeds Jolly Excadrill and with that Modest Lando/neutral-natured 100s. You can drop to 296 (160 EVs) if you just need to outspeed through Jolly normal Heracross/Kyurem-B. Beyond that you can run 279 (92 EVs), which is enough to outrun Timid Heatran along with Adamant Excadrill/Jolly MHera. More bulk is really nice for Mega Metagross because it is actually a really bulky Pokemon, so with investment it can take some serious pounding from resisted hits and tank some pretty strong hits. The bulkiest spread of the ones I listed (192 HP EVs) takes ~half from Mega Lopunny HJK and ~half from CB Azumarill Waterfall, for instance. Just some stuff to consider/mention.