If you're gonna go geared, and are not committed to an OG build, I'd get one of the long-cage Suntour rear derailleurs with the threaded claw. I think there were even claw-mount Cyclones. Vx-GT, for sure. Best-shifitng claw-mount derailleurs ever made, cheap and easy to find, and the derailleurs are exactly the same as the screw-mount versions.

Of course, there was a claw-mount long-cage Jubilee...

--Shannon