Clouds as transportations are already done and to be honest, there is already quite a lot of Aerclouds in the Aether... As for great reward... Well they ain't implemented yet so I'm not sure what will be in there but most of the dungeon rewards are good items. Maybe other then the Flaming sword, since unless if they change it a little, it's basically a wooden sword with Flaming aspect...
Oh yeah, forgot about this. Aether I was only singleplayer, so I'm thinking the bosses might have had the need to be balanced but now that you can have more then one player entering the same dungeon, it can be made a little bit OP and players can still defeat it.
Perhaps some boss that is actually that OP it would require a full party to defeat it?