For the doom wad selector... Can't you just write a *very* small app to rename one of the wads you have in your directory to the one the engine loads by default before you run doom? Or you can always add it to the engine itself, which would look a lot nicer. I forgot what it was like to play doom, my fps of choice was quake, where you could just load the mods by going:
"glqwcl.exe -game fortress" (loads the paks (equiv of wads)) from the fortress subdirectory of quake.