[user1007]

How, or were you going to anchor the deck to keep it moving in lateral directions? What about the 10" drop/step around the perimeter?

 

[user1007]

Apparently you can rent/buy “pool cover dance floors”.
Here’s just one.
http://theeventdepot.com/stage-dance-floor-rentals-in-miami.html

I wasn't trying to blow your concept apart by the way. I think it a fun idea.

These look kind of cool and I bet the event rental company would know what you needed in terms of liability insurance and so forth.