found a way to make oldDark and NewDark coexist peacefully in one Thief install. if you want to try it out, just extract
this archive to your TFixed Thief install, and run the legacy exe of your choice (THIEF_orig.EXE, or THIEF_ddfix.EXE). when running a legacy exe:
-mods will not be loaded, so you will get full vanilla looks
-gamesys/map fixes WILL be applied
-resolution is set to 1024*768, anything else might not work
-separate save folder will be used (so oldDark and NewDark saves won't mix)
-separate bind file will be used (so oldDark and NewDark binds won't mix)
-running oldDark should not break NewDark in any way, and vice versa
if found usable/stable, it will get included into the main TFix build.