I'll post my general idea as a placeholder, to see if I ever get it to actually work
![Tongue](https://forums.tigsource.com/Smileys/derek/tongue.gif)
I'm a big fan of Warning Forever for its series of bosses that get successively bigger and more dangerous in various ways depending on how you defeat them. I also played a lot of World of Warcraft with its big dungeon bosses that required coordination and teamwork to defeat. There's probably a good reason the two haven't been combined, but I'm going to do it anyway.
So the premise: player(s) run around in a sorta-randomly generated chamber, with a big "boss monster" in the middle. The boss is assembled Frankenstein-style out of disparate body parts (skull head, robot legs, etc.) Each body part has a special attack related to it. You can attack a body part and eventually disable its special attack. The boss is defeated when all body parts are disabled. When you defeat a boss, the next boss is similar to its predecessor but has one or more body parts "upgraded".
Step one is to build a simple "boss skeleton" and attempt to map some simple shapes (boxes, ellipsoids) to each bone. If that works it should be pretty easy to make a few simple body parts (arms, legs, head) and assemble the boss. The method isn't that different from a typical game that lets you customize your avatar, so hopefully this whole thing will be straightforward...