Yes, the game was a bit of a hassle to learn. But having played many 4x games (complicated) like X3 Reunion, Moo2 ,Gal Civ2 and the video tutorials helped me greatly.
Additional suggestions:


For ship designs: Still leave the core designs in place so that (default) players can jump in right away and ignore it if they want.

Additional planet types:
Asteroids- Mostly mining or outpost(should be rich in resources)
Dwarf Planets- Similar idea, maybe a small military base
Moons- Can build defense platforms on here to help defend planet.

Ships/Structures:
Corvettes
Starbases/ Orbital Commerce (Trade ports) or space docks.