Do it like GW2:

1 AH, all servers use it, so server location or even world your in means nothing to the economy.
Server Guest feature. Want to play with a friend on his server? Just "Guest" there.

That way you still have regional servers but you can still play with others anywhere XD

Or ya know, just realise 2.0 wont have 10k players and there will be several thousand online a time, regardless of how many servers. Plenty of peeps to hold hands with.