It'd be better if they just get rid of megas.
Or at least keep the ones we have, ADD NO MORE, and for the love of Beerus or Thor, please don't remove the need of having a mega stone. Mega Ray is still drinking a beer with SwagPlay Klefki and Minimize Smeargle. No but seriously, Mega Ray is stupidly overpowered, like what were they smoking when they made it?
Imagine Lum Berry DD MegaZard X. You can't paralyze it and stop it from sweeping, a solution many offensive teams use to stop it and other DD users. Basically you better pray you can set up rocks and keep them on (and by this logic we should unban Ho-oh, I guess) or have a scarfed base 100+ that hits hard enough to OHKO Zard X. Terrakion and (assuming it gets unbanned) Landorus-I are like the only one I can think of right now that are viable and can OHKO +1 Zard X without resorting to BS like using Slowbro or relying on Thunder Wave/Toxic/Flare Blitz recoil...
Or Choice Band Mega Medicham, like do I even need to tell you how retarded that would be? It'd probably be able to OHKO frickin' Hippowdon and possibly Suicune after SR damage!! We'd have to say "arigato gozaimasu" (or whatever the words are in JP) that Aegislash exists, and if it once again gets the boot, we'll basically have Mega Mawile on steroids, insta-Uber. Mega Gardevoir would be the same, although fortunately Chansey exists too.
There's also Mega Salamence in Ubers which would probably get the boot instantly with an item like Life Orb or Sky Plate. Just imagine a +1 Double-Edge with a LO boost. Not to mention how good Flying is as an offensive type, at least in Ubers where you have to rely on Aegislash or Dialga to tank such attacks (and btw Mence also gets EQ to squash them).
The good news is that I wouldn't see worse megas such as Audino or Abomasnow get the boot by just removing the mega stone. Also, I don't think Mega Diancie would be banned even if items were allowed; it still needs to use Protect, meaning it's very hard to slap Choice items on it, but crap LO M-Diancie would still hurt like hell. It'd surely be a top-tier threat if not for Aegislash/Weavile/Excadrill or something...