lots of balancing to be taken into account here, but that is a fun idea
the cave generation would obviously need to be adapted, and the lasers might be too much if they can target dwarves
the design could be very interesting though. It could be floating in the same way that core stones do, tying this into the upcoming themes of rogue core, but I feel like it would just be a mix of the current core spawn event and the mobile rockpox event.
what if the reason it's moving is because it grew out of the back of a large creature, say for example, an ebonite bulk detonator? now the first objective of immobilising it becomes more active. Maybe the legs have to be mined with power hits?
either, way, this is a fun idea to play with