Probably for the best that actual gear is never included in the Aquapolis, deeper or no. It really is a nice inclusive bit of content that you can drag anyone around to do, and the rewards kept to non-progressive items means the place will always be relevant in some fashion.

That said 7 floors is good, very good. There's a level of enjoyment that they hit just right with fighting RNG just getting to a 7th floor. It's a distance, but not overwhelming. Even if you only hit the 6th floor it's not nearly as disheartening as it would be if there were 100. Keeps a limit on what to expect and it feels good.

A deeper level for the truly masochistic to seek out wouldn't be a bad idea, though. Just no changes to where the current is now outside of loot updates in the future.