I wouldn't mind if outsiders came to see how its getting along on occasion, and were treated as such (I.E. people didn't treat them really well IC due to OOC friendship), but if they wanted to become a regular feature, PvP or have any kind of influence then they'd have to make new chars.

Most importantly, all IC authority from the old guilds would have to be meaningless in the new community. An outsider noble would be treated as lower than a peasant from within.