So I figured out a way to run the game at native resolution of my monitor by adding this to baldur.ini:
'Program Options', 'Graphics', 'Width', '2560',
'Program Options', 'Graphics', 'Height', '1440',
'Program Options', 'Graphics', 'Scale UI', '0',
And even though the game certainly looks much better in fullscreen than it did before (blurry blown out 720p, I believe), the menus are all weird.
Here's how that looks like: http://imgur.com/a/swIPm
I understand there must be a reason for the absence of resolution option (although I can't think of a good one), but it would sure be really nice to be able to play this game in 1:1 pixel ratio in full screen. The menus are all functional (apart from some scroll bars here and there) so if you could fix the messy backgrounds that would be much appreciated by players with larger monitors.
PS. Sorry if that's already been brought up. I tried searching, I swear.