Agh, you did that annoying thing where you reply in the quote and the coding on this site doesn't let you quote quotes...
Anyway:
1: Not talking about the aesthetics (except to concede that FC used them to help simplify things) so much as I'm talking about it getting confusing when every tournament has a different set of groups. Admittedly, it's a minor thing, but it's there.
2: If counterpick stages have 90% of the same traits, that's less a ruleset problem and more a problem with the part of the PMBR that designs stages. The beauty of playing a hacked game, eh? But seriously, we have a lot of Battlefield clones (BF, Randall, DL64, FoD, to a lesser extent Skyworld) or generally similar static or near-static flat-plat stages (PS1, PS2, Warioware, FD, Metal Cavern, and to a lesser extent GHZ, Drax, and SV).
We could conceivably fix this with the group ban system, but why not just use more varied stages?
In particular, move frozen PS2 over Flat Zone instead of over regular PS2 (which deserves a chance IMO), maybe give it a new texture and call it PS0 or something. Start using stages like PTAD, Delfino, and Norfair (nerf the hazards if you have to). Take Pipes' left half and reflect it so the walkoff is gone, maybe expand its blast zones a bit and get rid of the cave of life, and it's legit. Bring back Distant Planet, maybe giving it a similar treatment to Pipes (even if you just use the center platforms, the fact that they get lower when you land on them is very unique). Get rid of the bottom Spear Pillar platform, maybe change the way the background pokemon work, and it's another good stage.
Just some ideas, off the top of my head. Maybe they'll work, maybe they'll need tweaking. Point is, we have it in our power to make stages that aren't "90% the same".
Or do I have you backwards? It's hard to tell what you're talking about when you say "ban/CP invalidation" since ban invalidation and CP invalidation are opposed concepts. There's not really a difference between the community not using stages because they're scrubs, and having a lot of stages go unused because of the ruleset.
Basically, the way I see it, Smash has three unique things going for it, one of which is the stages (the other two are percents and DI which aren't relevant to this discussion). If stages are so similar that you have to ban several at once to make stage bans meaningful, I feel like we've lost something special. You follow?
We've never had a prominent Smash hack before. 64, Melee, and Brawl did not have developer support for competition or the ability to fix problems as they arose (merely compensate with rules). PM is a changeable game, so why not tinker around rather than try to cover a problem with more rules?
3: I preface basically all ruleset suggestions with "wait for the metagame to develop" when it comes to new or still-updating games like PM. Don't take it as anything overly significant.
4: Admittedly, it's slightly more complicated than simply having no groups, but more groups is more complicated.
And in reply to your replies to others, I don't see how "when you win, ban X number of stages" is more complicated than "you can ban these stages, these stages, these stages, or these stages", nor how regional differences in the groups is a good thing but regional differences in the number of bans is a bad thing.