We'll probably with get stuck with the lame scenario that the old versions aren't tracked in universe. Which means we will have to force them into storylines, but they can't really hold belts. And then putting the modern versions on dead brands really won't work so we'll still end up with Kane vs. Kane, Undertaker vs. Undertaker, Helmsley vs. Triple H. vs. Triple H, Mankind vs. Cactus Jack vs. Mick Foley, Y2J vs. Chris Jericho, etc...