Hmmm, earlier in the thread someone mention the possibility of having a starbase in orbit around a planet and being able to use that instead of the planetary starport. I could see this being a useful game mechanic to save some terrain on low quality planets. A "planetary Starbase" could be limited to to the types of available expansion options, or it could act as a normal starbase that allows the planet below to have the benefits of a starport.
I really like the ability for a constructor ship to carry multiple modules. Being able to "repair" it at a home planet would be a nice additional option to restock the modules for further work.
I would change the mechanics to disallow any constructor to be upgraded in open space, requiring that they have access to a planet to refit or restock. I've always thought it useful but very cheesy to flip a scout into a constructor via an upgrade when it was in empty deep space. ("yeah, let's refit those ion canons into a 3d printer while we hang here")
Another point someone brought up was the possibility of a trade module for a starbase that produced BC's directly for the station, rather than one that simply assisted the routes that went through the area or increased the planetary production rate. This "trading post" concept could produce a small fixed amount of income in the absence of trading routes. Something akin to the restaurants and hotels that the railroads built to earn extra income at their stops. The income earned of a trading post could vary somewhat, depending on the amount of tourism, proximity to a planet and other relevant factors.