[JenMax]

I don't know if this is do-able. If you want to reduce supplies carried by each engine, and you vary the amount of supplies carried by engine type, (your example, solid fuel inside "stores" more supplies), THEN you might also want to vary how much each TYPE of engine regenerates fuel per turn. Ion engines might get a bit of "fuel" based upon suns in system (amount of "ions" floating about to 'grab'), or allow some types of engines to "refuel" by skimming gas giants...(not original idea - read in book 20 years ago... ee doc smith maybe?). What do you think of this type of add on to engines?