Some of these ideas are essentially doable in the modding of DoomRL.
Thus far, traits, classes, and the like are unmoddable. But the enemies, weapons, items, etc are totally doable. Check the sandbox mode in the latest release, and follow the tutorial for the Q2Demo on the wiki and to learn the scripting, plus look at all the other things you can do but aren't totally described. Would be interested in playing your mods if you pull them off.