Had an opportunity to do a little more testing and I encountered a big inconvenience.
As soon as you get a player on a server that doesn't have a main character assigned the game forces the host client into the character assign menu with an error saying "Each player must have a main character assigned". Since there's only two "main" characters you can't satisfy the game's condition of assigning a "main" character to each player. The game lets you use the menu to assign characters as you please, but it won't let you leave it until each player on the server has a main character assigned.
The current "workaround" I got is making the server 5 players. The person hosting must then start a 2nd client of the game and connect to their own server locally. You then assign a character to each client and keep the hos client with no characters. Saving the game would be a problem though I think.
