As for multiplayer support, I'm all for it. Although I will buy Coldstone regardless, this would be, in my opinion, a very worthy feature. Perhaps it is too late, because, as you suggested, the game IS in beta 2, and many fans are eager for its release. I'm one of them. However, perhaps this could be an add-on or extended engine for the game.
As for the coding, I'm no programmer, but I doubt it would require so much of a change that you must rewrite the whole engine. Online games are not cutting edge; I remember an online RPG from Bungie several years back (1996 maybe?). The name fails me. They had nowhere near the edge available today, so it is possible. It consisted of a dungeon romp in which you could collect items and then battle your friends simultaneously. Even a primitive multiplayer engine such as this would suffice many needs, although many hope for something more sophisticated.
Considering server space, one should not worry when the game is not complete. Multiplayer could be perhaps only hosted on a LAN, or pier-to-pier computer connections. Even with plans for server space (which I approve), it would not be impossible. There are MANY hosts on the web, some free, others charge, but none are out of reach. Even Ambrosia could cash in with its own hosting service plan. Since all will be buying Coldstone, it's not as if anyone here is without cash. Ambrosia could easily expand to offer hosting services for various needs, at different costs. Please keep an open mind to these suggestions.
~Saphfire