I have one more point to make:
I remember during Baton Pass Clause, where tier leaders [originally] voted for an in-battle clause despite overwhelming PR support for a teambuilder clause (edit: apparently this was just a misunderstanding). I think this is because they looked at it from the perspective of a user who already knows everything about Smogon and the rules from each tier, and didn't consider how confusing it would be to a user new to the tier.
I see the same idea here. To an experienced Smogon user, the rules of each tier are easy enough, it's only one or two bans every few months. To a newcomer to RU, though, should they really be expected to keep track of which mon is RU because its mega is banned in a higher tier, and which mon is RU because its mega is actually usable there? This is information that the teambuilder's tier list can easily convey, but by banning mega stones instead of tiering megas or tiering their base forms, the teambuilder can't convey this information and the users lose.
As Smogon users, you're responsible mostly for other Smogon users, but I have to be responsible for the PS users who aren't as involved with Smogon, and I think this issue disproportionately hurts them. Please, think of the children.
(And yes, I'm fine with waiting until after Grand Slam.)