hehe... I've done stuff in the regen path on accident. I tried an active clipper section. It sounded kinda neat, every repeat would become more distorted and closer to a "failing transistor radio" sound. I used a BMP clipper stage, ironically. Maybe we should just try an entire BMP in there, lol. Seriously, that could be something useable by bassists... Clean, no delay sound, with this repeated crap happening in the background.
The BMP stage got me thinking about trying an octave up in regen, but I've never got around to it... so there's an idea for you.