Baseline (Widescreen) Solution & Issues
Limited to a set of predefined resolutions by default.
The workaround for hor+ scaling of the world view is as follows:
Make sure you have created a profile and set the graphics the way you want them.
After that, quit the game and go to <gameDir>\etmain\profiles\<profileName>, and edit etconfig.cfg.
Modify these lines.
seta r_mode "x"
Set this to -1.
seta r_customwidth "xxxx"
seta r_customheight "xxx"
Set this to the desired widescreen resolution.
seta cg_fov "90"
Change the value to that of your resolution as guided by the WSGF FOV calc or as preferred. 100.39 for 16:10 resolutions and 106.27 for 16:9 resolutions correspond to 90 at 4:3.
The solution does not address the UI stretching and the viewmodel cropping, however, the game allows to set the crosshair to be a dot, which may help mitigate the stretching.
Ultra/Super-Wide (21:9/32:9) Specific Solution & Issues
Same issues and solution as for widescreen.
seta cg_fov "121.28" at 2560x1080 would match the default of 90 at 4:3.
Eyefinity / Surround Specific Solution & Issues
4k UHD Specific Solution & Issues