[xyzw12345]

I can't say i've done internal modelling for a battlestar but i have built a frigate class starship inside and out. The hardest part is actually using all the space available because where you have curved hull surfaces you end up with curved rooms inside those sections which are really hard to work with and fill efficiently. On a battlestar that might not be so much trouble as on a frigate because the battlestar is so much larger ship and the curves will therefore be easier to just fit square rooms next to without losing so much space. A useful trick for armouring is to break the craft into internal sections, the most important of which almost have their own "hull inside a hull". Those crucial sections will be the bridge (or CIC) and things like the reactors. Ofcourse for really good full interior design don't forget the fuel tanks needed to keep Tsiolkovsky happy...

I do find it a shame that almost never does a sci-fi film or tv series fully address the interior layout of their key ships, one would think the writers and concept artists could work that sort of stuff out but instead rooms just fit together willy-nilly rather than how the hull around them demands(atleast on smaller vessels).