Yes. It's been done, in fact. In CHIKARA, Dasher Hatfield has had four personalities - Create-A-Wrestler, a play on the generic CAW from your average wrestling game, MosCow the Communist Bovine, which I think explains itself, Ultimo Breakfast, whose gimmick was, er, breakfast, and Dasher Hatfield, a play on old time baseball. He switched between these personalities once a year since his debut, until the Dasher Hatfield gimmick caught fire (and was in a tag team). In a match where he reverted to CAW, he ran through all his gimmicks and eventually became Dasher Hatfield for good, in one match, very similar to Mick Foley's triple Royal Rumble appearance. So, yes, it most certainly can be done. It takes a very special set of circumstances and a very talented wrestler to pull it off, but it can be done.
As for if it could happen on the mainstream scale, i.e., WWE or TNA...it would be difficult. I think the important thing would be not to force it. Mick Foley's multiple personalities were never forced, they emerged organically as the situation demanded. If anyone went in with the plan of creating a guy with multiple personalities, it probably wouldn't work. Although, that was always the intent behind the Dasher Hatfield character, and it worked out, so perhaps it could. Perhaps the most important element is not rushing it, which neither Foley or Hatfield did. I think perhaps being too heavy handed, pushing it, and switching too rapidly would doom the gimmick.
I could see it being done again, though, and while it would certainly have to be seen as referential to Foley, I think it could be done without being a blatant rip off. R-Truth strikes me as an obvious candidate, since he's already crazy. Mayhaps a guy like Brodus Clay might pull it off. Funkasaurus, and monster, and, I don't know, professional golfer, or something. I worry primarily that the WWE would blow their wad on it way too early, have everyone talk about it constantly, and kill it. TNA would probably wander off in the middle of it and forget who they were pushing too begin with, but again, they could do it. Eric Young already has a ton of previous personalities he could draw off. Someone like Robbie E who desperately needs to find relevance again could try it. Again, I worry about TNA's ability to maintain it long term.
So, could it be done? Sure. Get the right guy, the right set of personalities, and get the timing and execution down, and it would probably work brilliantly. I worry about the feasibility of those options coming together, however, in the mainstream wrestling companies of today.