To sort of add to the locking players in their seats, I don't know if any power type blocks will function properly while in motion like ic2 cables or thermal expansion conduits, so the craft might need its own miniature fusion and fission reactors thrusters and ion thrusters and methods of transmitting power or fuel.
Spell systems seem to be one of the hardest things to do right but ars and Minegica II seem to be the best two examples so far.
It could be done, That is what I was thinking, the code could check for all the required parts (like a builder did to recreate a structure) and allow it to move based off what parts were added, of course a power room, the core could be multiblock as well which would allow for larger cores, aka you could make mini-ships like fighters or transports that could have smaller cores that produce a lessened amount of energy. Tho I am thinking that players could make a smaller ship with a larger core to get more thrust to their engines and whatnot, aka there would be many modular parts to the construction and the player just builds the frame. Frames acomplished moving entire structures around with mod equipment I dont see any reason why this couldn't make a similar thing. Tho frames are so clunky and akward. I'd love to see a full space exploration mod that could easily bring a player from minecraftia (terra) to wherever. There could be scanning devices or even telescope based equipment that would allow for the scanning to find other planets, those other planets could be randomly generated or with another block (star charts perhaps?) could make their own planet based on a system like mystcraft.
The ships could have hyperdrives that would allow for instant travel from where ever you were to that location tho you couldn't go unless it was explored. You can scan distant solar systems based on your equipment and upgrades to said device in an IC2 way of upgrades. Local scanning wouldn't take much tho so you could easily find asteroids that hold materials and the materials would equal the size, so diamond asteroids would be massive with many different minerals while things like comets would have water/ice base materials and nothing TOO advanced (cause yanno.. comets dont host as many complex minerals as leftover star materials)
There could be star harvesting for power either the solar type or even so close as syphoning star material to power your hyperdrives (a basic one would need a lot of power but an advanced one would need a massive amount of power which would require upgrades and star harvesting.) There could be battles of course, pulse guns, lasers, missles, going wild and designing your own. Making a missle would only require a warhead and a rocket which could be manufactured somewhat cheaply. There would also be teleportation of course, that is how you would load into worlds, hop down and mine the materials to your heart's content then warp back up and move to the next planet.