Have been reading this thread for a while and enjoying the speculation!!
Thought i would add my idea....
Have any of you considered use of some kind of goodyear or similar heavy lift type blimp?
Imagine you could float it in to position high up in the air on the night, hook it up to an anchor cable/s (with a fireproof section half way up the cable.
a delicate design of cauldron could be winched half way up the cable with some kind of flexible gas line to the ground.
with the right lighting at night / colours of the line and blimp, it could almost appear to float in mid air
if it doesnt happen this games, i copyright the idea for the for future