[Edi]

There is a problem with the implementation side with the bitmasks getting really ridiculous. Bordermountain is already a very long bitmask and they would simply keep getting longer. I suppose it could be done, but it ain't going to be user friendly. That's assuming that the extra long bitmasks are not going to break something else.

The alternative would be some modification on how the land sea division is done and each of those having its own bitmasks, but that would not be backwards compatible and all existing maps would have to be redone. So while this thread subject is very interesting, it does pose a set of possibly non-trivial issues.