A world made of 1 metre cube blocks (which can hang in mid air with no apparent support) is not very realistic.
I'm happy with things as they are. The Fuel is an abstraction for the complexities that would be involved in real life - as I see it, it's intended to be RP-1 if made in a Refinery or compressed liquid methane if made in a Gas Liquefier. Those two are fairly similar fuels, although chemically different of course. My guess is that in real life a rocket which uses one as propellant could also use the other one, with little or no adaptation.
I appreciate that now that we have Liquid Oxygen in the game it would be
possible to add a liquid oxygen tank to every rocket tier, and a liquid oxygen loading machine etc, but I don't really see much point. It's two more machines for beginning players to build before they can get into space, but no obstacle to more advanced players who can make infinite Liquid Oxygen for free.
For Galacticraft's future I am much more interested in:
- developments connected with living in space and building sustainable space bases including food requirements etc
- optionally, more realistic handling of water and water requirements in space (see also notes here:
http://wiki.micdoodle8.com/wiki/Game_Balance#Hard_Mode)