I made an account here just to agree that this is a great idea!
The reasons this content is what the mod team shold spend their time adding instead of other stuff is that this will add a new realm of construction to the game, both aesthetically and practically. It will extend the range of the player, allowing for more exploration and settlements that are further apart.
Here are my thoughts on implementation, though recognize that I think it's a good idea even if it isn't done exactly in this way:
construction requires the crafting of many sections of canvas-to be combined into a ballon of one of three sizes, increasing in expense and size exponentially.
a basket (same idea. smallest basket goes with smallest balloon, and is only big enough for one person. Biggest is like a room with a balcony and a glass floor.)
and an engine.
To control the engines, the player crafts a control, which can be used within x blocks of the basket, and which steers it like a boat, but with up and down controls.
The engines cost coal to work, but will accept other fuels as well.