Hopefully Greg adds planet dimensions reachable through space rockets, the moon and mars?
So we may "fly" to the moon using space rockets ?
My suggestion is :
Space rocket is able to fly 250 blocks per second to the sky. Once it reaches a certain Y value (about 15000) you will get "teleported" to the moon at Y 15000, facing downwards.
Once in the moon, you must use air cells or you will drown (out of air). Quantum suit auto-uses aircells. Air cell should only be obtainable with water (or byproducts).
If mars gets added, steve must make Space Rocket Mk2 (speed is 350 blocks per second) in the moon, then "fly" to there the same way he did to reach the moon. (Reach Y 30000)
Space rocket Mk1 is Earth <-> Moon, while Mk2 is Moon <-> Mars.
If you are insane enough, you can try reaching 15000/30000 Y with gravisuit or any flying device, but you will run out of energy (or get bored).