Hey, I thought KOF XI was pretty great. I definitely agree on its graphical "flat"-ness, though. But that doesn't mean you couldn't make a KOF game with excellent movement, sound, pacing AND tagging.
I'd also love to see tag return at some point. If it did, I'd prefer to have your teammates standing in the background (a la KOF94-98) rather than simply off-screen. Graphically, I want tagging to look similar to plane-shifting from Fatal Fury, or how classic KOFs had your teammates coming in to save you when stunned. I think this could keep the characters "weighted" and prevent them from looking as "flat" as in XI. (At least, if I understood what you meant by flat.)
Oh, I don't mind them jumping in from off screen that much (though I'd prefer seeing the teammates, just dunno how it'd work)... things in XI were made with the ideas that impacts had to be swift, and easily-shiftable by multiple characters in mind. This brought on soooo many changes, not just to hitstun, but also the amount of time given for moves to linger, the length of sound effects, the flow of combat... what made XI's tag work, were a bunch of features that are cool by themselves (I really liked them in NGBC!) but they're not very KoF. Or should we say, they're not the best of SNK(P).
Pretty much everything that helped in the OP characts of that game, were due to the tag system DEMANDING changes for things like saving shifts and tag combos to work.
Also, I don't think including tagging as an optional feature is a good idea. It would be much more likely to be buggy and unbalanced. Besides, it's much easier to turn a tagging game into a 3v3 format, rather than take a 3v3 game and tack-on tagging. /OT
So, you worry that including Tag... would make it work like XI did anyway, eh?

I agree that it's easier to add 3 on 3 to Tag already, but I don't really care, lol. It's not exactly anywho; all the weaker aspects of XI's systems come right into 3 on 3 mode. I'd actually desire to see both done right, really. If they could get it all right, I actually think it'd be a great bonus. Weld be kinda like DoA2, where the tag modes and 1 on 1 fighting both felt like completly acceptable modes to play with everyone.
I'd still like a character that brings a "tag" aspect with them, that doesn't break the game, though. Like the TFADL / TFTP people all working together as 1 or 2 spots on a 3 man team. While it could turn out disasterous (like that guy from Sam-Sho V with the henchmen), it could also turn out very cool and enjoyable (like Doronjo from Tatsu VS Capcom), and that's what I'd be hoping for.
I love this series. Haregoro proves again that Joe is a killing machine. Leona shows off a Takuma-specific 100%. Ralf's HD corner juggle was also really good. I hardly see Ralf use HD, but it seemed really practical. Just qcb+A / AC and qcf+P (A? C?) a lot.
It's the kidna thing I always expect to scare new players away (How long did that combo take? WHY DO I WANT TO PLAY THIS?!?!), but they normally seem to be well understood. I really enjoyed all the "using specials as a form of movement" stuff, it seems like one of the good holdovers from XI (things never recovered this fast in the past!) that I can actually deal with in XIII!
Some of the Frionnel matches were really fast and aggressive, that's what I love to see in Kof matches.
I know, it makes the game look totally different than watching people who don't know KoF as well play. It's quite enjoyable, and I think it really shows "KoF-ISM" at it's best. There's an agression, mixed with ability to excape (by spending meter) that no other game balances as well.