Just a quick idea I wanted to throw out there...
How about a mod to go hand in hand with a landmass mod, that removes the landmass but keeps all the custom items, etc. from that mod?
So if there are 2 conflicting landmass mods you want to play, you can play one, sink the island with a separate plugin file, then play the other, while keeping your items from the first.
What do you think?
- Danjb