I would like to suggest having a list filter in the ship design screen, next to the race filter, to split the list of ships into military, fighters, missiles, PDCs, civilian(crown), civilian(private), and replace the show civilian design tickbox to show foreign designs.
I would also like:
-Something similar to planetary defence centres, but not armoured like a nuclear bomb shelter. These could be built by a construction brigade out of dirt, snow or rock found in the area, with a few resources for components. Another possible feature is to have them be similar to a fortress network (like the Atlantic Wall or Maginot Line) facing an enemy, which could be expanded upon as you add more 'components' to said network.
-Components for said construction, such as airfields and hangars(cheap, cheap space for fighters), ammo dumps (cheap space for munitions, but stored like cargo), casemates (weapon positions similar to turrets on ships, but cheaper) OP/FOB/Fort (fortified fighting positions to increase the defence against land assaults), bunkers (to house and protect ground units from bombing), etc.
-The ability to classify a planet as an outpost, which would limit the total population to a small size.