[Rupert]

One thing to consider is what sort of shiny spaceships you want the system to encourage. Do you want a setting where it's "WWI in space"? Or "WWII in space?" Or maybe "The Cold War in space" or "galleys in space".

This often boils down to it being a 'big ship' or a 'small ship' setting. One where ships can carry weapons that easily destroy other ships regardless of size will encourage small (and thus cheap) ships. One where only big ships can hurt other big ships will tend towards warships becoming as large as the governments paying for them can afford, assuming no other limited exists.

As all spacecraft are moving through the same medium (magical drives aside), the aircraft vs ship distinction that so affected WWII naval warfare doesn't apply, so getting 'WWII in space' requires some fairly arbitrary rules and/or technological features, and is very hard to balance so that it's vaguely balanced and fun. Of course, if you're planning a game where everything is in transition to (or from) carriers, this won't be a problem.

Most WWII in space rules I've seen seem to expect it to be a sort of steady state, where powers will be battlestarships and carriers plus their 'fighters' and they'll all be useful. They'll probably have some sort of battlecarrier with fighters and guns in there too, and the rules will bend around it to make it actually useful.