Why do you want multiple character servers?
The problem with multiple character server connected to one map server is that the map server assumes there's one character server, so when the map server needs something from the character server, there's only one file descriptor. If you have multiple character servers, you'd have to store the which fd a character is loaded from, then use that fd.
Another problem is if you have multiple character servers, they could use the same ids for characters, parties, guilds, etc, which will result in some undefined behavior.