Currently at work so I'm not doing much with this at the moment.

I did however play around with it a little more yesterday to see if I could break the interface to prevent the error from coming up. Here's what I learned.

I extracted the "Game.pak" file and located the GUI elements for this menu. If you extract the pak, they will be located in the Public/Game/GUI folder. They appear to use flash (.swf) files with scripting. The two files utilized in this menu are "characterAssign.swf" and "msgBox.swf". There are also 2 similarly named files for the controller UI.

characterAssign is the menu used to control assignment of characters. The msgBox is used in various places around the game, such as the exit game prompt, the "Server shutting down" notification, and of course the error preventing you from leaving the assign screen when a play doesn't have a main character assigned.

Replacing characterAssign with another .swf file to produce results like this: http://i.imgur.com/t4MZjeW.png. Of course there was still no way to escape from that menu.

I tried decompiling the characterAssign.swf in hopes of being able to break the scripting that calls for main character verification, but flash decompilers are spotty at best, and editing anything in a meaningful way is even more so arcane.

I then had this brilliant idea of taking the characterAssign menu from the original game and putting it into the EE. Unfortunately, that didn't work either. The menu works fine, but the error still pops up as normal. This leads me to believe the check isn't called from a flash script, but done elsewhere in the game engine.

At this point the only thing I can think of is using a debugger to find and then break the JMP that executes the main character check. I don't know if I'd have any luck with that and honestly I'm not sure if I should purse that either.

Either someone smarter will figure this out, or we'll have to wait for Larian to release the official tools. Didn't look like that was happening soon. I have a slim hope that someone from Larian will read it and help us out by removing the "main character" restriction next patch, but I'm not holding my breath.