Suppose once players reached a certain accomplishment our account could get bonked on the head and split into more identities with zero accomplishments and some variance in the starting skills/characters of the new idents. I'm not talking about new accounts but an alternate identity that the players could switch to, to replay the old challenges that they've already beaten and build up the second ident.

Then we could be 2 identities with one account, and we could switch back and forth between the identities...like a schizophrenic. We'd have our first ident with its advanced talents and our noob ident both under one account.

I suppose you could also give some advantages to the new ident -- or disadvantages. Another thought is to start the new ident with a different starting set of characters.