If Ubers were allowed, there would need to be a minimum base stat. As it is the lowest seen in game (bar Shedinja's special case of 1 HP), I vote that the cap should be 5. The only issue I see is with the banned mega stones. If the same policies regarding low-tiered pokemon with banned mega stones remain in place, then the NU Kanga could mega-evolve into a behemoth with 120/140/115/75/115/115 base stats and Parental Bond (producing essentially 235 base attack when using a jolly nature). Something would need to change, because not even Furfrou is walling that at +2 attack. The following calculation is with the TS BSTs:Gorebyss hello? Gorebyss is an absolute BEAST in tier shift it can smashpass just smash and sweep or even both, amazing mon one of the best in the tier. Also one mon i have had my sights set on is dugtrio. All dugtrio wanted was some extra firepower and it got that along with the bulk to survive a few more hits it is still frail but it is really improved. On yet another note we were talking about unbanning ubers and giving them -20 in the om room and it seems like a good idea imo, deoxys a has 0 defenses literally lol.
+2 252 Atk Parental Bond Mega Kangaskhan Return vs. 252 HP / 252+ Def Fur Coat Furfrou: 228-268 (59.3 - 69.7%) -- guaranteed 2HKO after Leftovers recovery
Aside from that (and potentially Mega-Gengar, though that's far less of a problem), the ubers with -20 idea sounds pretty cool. Now that I think about it, the Mega Mewtwos could also potentially be broken. All of this would have to be tested, of course, but these were just my first thoughts