be able to save a half-built ship design rather than having to finish it in a single sitting
highlighting which parts are triggering a particular error or warning
all parts you’ve encountered to be visible in the build lists even if they’re not available at the current shipyard, marked as not available but with a way to see which shipyard has them
a way to override the automatic placement of doors and ladders
a way to do a walkthrough of the partially built interior of a ship so you can see how the layout works before having to fit engines, gear, fuel tanks, etc
some way for players to share / trade ship designs
I feel like Bethesda has released the game with Minimum Viable Product systems in some areas (ship-building, outpost-building, inventory management in particular) knowing that the modding community will massively improve the barebones.