Please add the ability to tell a planets shipyard to work on ship upgrades instead of building ships or doing nothing. I dont mind if it takes rather long compared to the current upgrade of ships (loads of cash + 1-2 rounds usually), but if you upgrade a lot of big ships it simply costs too much. Why not make use of them shipyards for it?
1- Good idea, and I would go further. How can a starfighter with, let say, 2 lasers upgrade itself alone, lost in space, to a starfighter with 4 lasers? I would disable the upgrade feature unless present at a starport. I wouldn't change a thing about the price and the upgrade time, but there could be a planetary improvement named "Starship Factory" that could lower the price and accelerate the upgrade time on that particular planet. That could become a nice strategic option.
2- Another thing. That would be nice to display repair circles when selecting a planet (well, cases next to the planet). That would allow the player to move is damaged ships in the repair circle of the planet and still receive the repair acceleration bonus. We could assume that because the ship is next to the planet, the starport operators are auto-managing the ships in orbit for repairs, leaving some space in the starport for new constructed ships. And all this explanation to introduce my idea: allies and friend civs could help repair your ships! Just leave it next to your ally's planet and it repairs. That would really be a great addition, especially when you send your fleets to protect your ally homeworld !! Also, that could be extended to military starbases.
3- Taking both above, the creation of a new "Shipyard Starbase". It would allow you to repair ships faster, upgrade ships and of course, build ships near your enemy ! To that, many ideas are popping in my head:
- Could have a "Supply route" in order to acquire materials. This route could be something new, of simply a Trade Route sacrified to the cause.
- Could have a new starship module "Cargo hold" making a ship an official supplier for the bases. Could be managed by a new window "Supply Route" and could be target in war time, disabling a shipyard starbase after some time.
- Could just be a normal starbase.
- Could be the target destination of asteroid mining bases.
Maybe the last one is too big for a patch and would require a expansion pack. But hey, you guys decide

sooooo many ideas !!