So I've been testing out meshes in the demo, and came across a surprising and disappointing limitation.
The 3d models for fighters are only used for ground combat, not space combat. Space combat uses sprites from the Empire_Unit_Combat_Texture file. Not a bad idea in theory, as it keeps the poly counts in space combat down. The problem is that the code for determining which sprite to use is tied not to the individual vehicle size/class (such as small fighter, medium fighter, etc.) as defined by the vehiclesizes.txt and Empire_Ships_xfileclasses.txt but to the overall unit type (i.e. "Fighter") as defined in vehicleunittypes.txt . This means that currently you can only have one image displayed in the tactical combat screen for all of your different fighter types, a step backwards from SE4. It makes it very confusing when you can't tell the difference between your light space-superiority fighters and your heavy anti-ship bombers.
I suspect it will be a long while before we can get it changed so the sprites are assigned by the ships_xfileclasses file instead.