I've compiled an easy Widescreen fix pack for this game.

Contents:
Resolution set to 1920x1080
FOV increased to 113.5
Texture cache updated to 1024 MB from 32 MB
Widescreen HUD texture fix v1.1 by Celidor
Bumpmapping set to low

Here's the download:
https://mega.co.nz/#!TQMyzKbD!oz_-GUN3PoOIg-J5bc9hKfSNywVnt-gYbXDX-LoTOXA

If you want to change resolution:
[url=http://pcgamingwiki.com/wiki/Star_Wars:_Republic_Commando#Widescreen_resolution]http://pcgamingwiki.com/wiki/Star_Wars:_Republic_Commando#Widescreen_resolution[/url]

If you want to change FOV:
[url=http://pcgamingwiki.com/wiki/Star_Wars:_Republic_Commando#Field_of_view_.28FOV.29]http://pcgamingwiki.com/wiki/Star_Wars:_Republic_Commando#Field_of_view_.28FOV.29[/url]

Thanks to CyklonDX for some much needed tweaks.

This is working great. I even used downscaling and the game looks great. But after each new level the bump mapping gets set back to high and after another level has been loaded my viewsreen is completely white. I than have to exit the game and reload my savegame. The view is ok until it starts again as described.

Any ideas?

Make sure you aren't modifying any game settings through the game itself after this fix. Any settings you want to change should be done only through the System.ini file located in GameData/Save. You should set the System.ini to read only after you change all the settings to your liking.

If the game crashes on startup like in my case just copy the engine.u and hudtextures.utx to their folders and edit the resolution lines in system.ini yourself in your own original system.ini.

for 1080p it's the following (below [WinDrv.WindowsClient] )

WindowedViewportX=1920
WindowedViewportY=1080
FullscreenViewportX=1920
FullscreenViewportY=1080