Have you tried Radiant 202? It was the last MFC build before the dark times. You'll have to do some gymnastics with texture folders and sleepwalkr's mapconv.exe to use it for quake1 but once you've set it up it becomes an invisible part of the process.
sikkpin also updated the original QE quite a bit, and that's still MFC so it might also be adequately windows future-proof. Works great on 7, at least, and it's what I use. Harder to find, but still essentially Radiant.
Nope. I can't install the 202 on Windows 8.1.
The installer won't start.