Still dont know if we want to have an actual fuel source, but it is definitely being considered, and i am a bit of a scifi geek when it comes to crystals and tech (crystaline everything in a space ship!!!)
Throughout the years, crystals have been theorized as providing some use in scientific development. take the quartz clock for example. Personally, I find the use of crystals for power as an overall ingenious idea, although how to implement them would require strenuous balancing. However, power not only works in x,y, and z. it also works in straight lines and for really huge vessels, in 10x10x10 blocks. I would agree with wizard if it were not for the fact that power in it\'s current format is indeed limitless in ideas for crafting a ship. it\'s what you do with them that limits their usefulness.
I would like refueling a lot too. You could even let the normal power blocks as they are. Just make it so that the perform on 10% efficency when no fuel is there. This way we would have a lot of potential for role play. You would need factions or people in a faction why mine fuel. You would need to protect the stations.
we could have fuel stations in orbit of gas giants that provide fuel for the faction that owns them.