I run a triple 2048x1152 monitor setup, for a total resolution of 6144x1152.
Will there ever be multi monitor support?
Will you allow custom resoluitons, or atleast add more to the list?

Actually the game supports custom resolutions.
But it requires some ini-file magic.
1) you need to create a file named user.ini in the game root folder
2) add the following lines to a newly created file:

[unigine settings]
video_mode=-1
video_width=6144
video_height=1152

3) save it and start the game.

Since now you might not be able to use launcher or ingame resolution setting.