Love the mod (surely you've seen my posts about it in other threads
).
I'm just going to repeat a suggestion I saw a while ago:
A customizable world-type, done like an Enscriber.
Think like superflat, but instead of needing a complicated set of codes, just set up your dimlets (which are infinite and searchable) inside of a "Custom" menu under the "RFTools Gen" worldtype. So, if I want floating islands with liquid orbs of oil, I can generate that as my overworld. ^^
A couple presets would be good; fantastic overworld with extra dungeons and nether biomes as well, and maybe a mining dimension - increased oregen with the cavern worldtype.
I plan on trying to implement this myself as part of a mod I'd *like* to make, if/when I actually learn to mod properly.