So I think a new system of air should be added. The world would by default be breathable, but events should be added for zone blocks that make it so that there is NO air inside the zone would be cool. And along with that a new system for air (underwater OR space themed) that doesn't have an air meter that is bubbles (so that it can be better space themed) and have masks that keep your air level from going down. So basically this new air system should have:
-events to control breathability inside zone blocks
-new air meter to allow for better themed games (as opposed to the old bubble one, but still works the same)
-A space helmet and/or a scuba helmet (OR an oxygen mask) that keeps the air meter from going down
-and maybe a player type that isn't affected by air