I have an outline and story for a completely different non violent shard based game that would benefit from licensing the plasma engine from Cyan, but they gave me a flat and quick NO when I asked about it. Apparently they just are not interested in licensing the engine even for something outside the Myst universe. It is their ball and they don't want anyone else playing with it.

Technically anything that is more than MO:UL or more than UntilUru is MO:RE so I believe the discussion belongs here (that's an opinion not a ruling).
Alcugs may be flaky/buggy in places and come with it's own set of problems but it is probably closer than any other start point. Until Cyan come out of the woodwork and give us some information it's not going to do any harm to kick the idea around to see where it leaks.