from what I understand by reading the code: theres a middle layer between the texture and the native resolution, so you can view low-resolution textures also going to choose a high resolution
I think this is a bad thing.
the first thing is to eliminate this intermediate layer, so doing openxcom only work in native resolution (320x200 I think).
as a next step is to go to support different resolutions deciding screen by screen which components should be expanded and which should be fixed length.
As a general rule: the buttons and HUD must be fixed, others can be expanded
I can help, but I can not coordinate this because I do not know enough about the openxcom source code