Seems as it's going to be a fun encounter.Nice job on the mapping.
If I were you I would make the rotating of the rings take 3 combat turns in which every combatant will be slowed(effect stopping after the rotation ends )and at the start of each combatant's turn to be slided 3 squares depending on the rotation of the ring and that movement because it's forced movement won't cause any attacks of opportunity. But that's just my opinion.

P.S. You're lucky that's intended for a virtual tabletop cause imagine printing that map 8 times.So much ink spent.