I mean, I get the concept of how it works. I'm just wondering about how believable that is (to the extent any of this is). If I was building a starbase in the Galciv fictional universe, I'd think I'd have materials delivered via transport ships from my planets and assembled on site by construction bees. 

Or treat Starbases like Planets and give them a build queue.

Then you have to ship them supplies that are built on a nearby (or distant if you like) planet.

Perhaps a system could be created where, for every starbase, the player establishes supply routes from a nearby planet or planets.  It could operate much like a trade route, except the shorter the better.  Once a supply route (or routes) is set up, then a portion of the industry from the route's origin would be sent to the starbase for use in building upgrades.  The greater the industrial base on the originating planet, or the more routes you establish, the faster upgrades can be built.  For really distant bases, the option to build and send a constructor for an instant upgrade could be retained.

I, for one, absolutely loathed the constructor spam part of GalCiv 2, and it's the number one reason why I don't play it any more.  We can do better.

Agreed, Constructor spam really did just get to be too much after a while.  I frequently did cultural domination backed by a big fleet, and to do the starbase walk was tedius.  I know that starbases shouldn't be able to be built and rebuilt instantly, BUT, there needs to be a better way than that.

Also, in late game when everyones techs were really solid, a completely maxxed out military starbase was a VERY easy target for anyone with a descent fleet.  I think being able to attach fleets to them is an excellent idea.

I know it was mentioned earlier, the varying types of starbases and that political bases shouldn't be armed, I disagree. B5 has been used as an example many times in these forums, it was a political base in neutral territory to help resolve conflicts before they turned into a shooting war, and, it was still armed to the teeth.  Im sure there were major bases that outgunned it, especially military bases, but I think the political center should be able to protect itself as well.  A military base should be better armed though.

I have a idea for a new type of base altogether.  Shipyards/Docks.  Something purposely built to crankout ships and to repair them as needed.  Say I have a destroyer and 3 Corvettes left over from some battle and they are hammered, get them to the dock, they then sit in a defensive perimeter and wait their turn for a repair.  Still usable in defense of that base until it is in for repair itself.  The shipyard portion can also be used standalone as a builder for ships as well as a repair facility.  Possibly upgrade the facility to accomodate larger and lareger ships, modules for faster or more effecient production, as well as able to make different ships at once, based on the shipyards facilities.  As for how you make 3 ships at once say, I am thinking somehitng like the base in the opening cinimatic from MOO2, just the look, the 3 platforms around the perimeter, build a ship on each.

The constructor spam was annoying, but I think I'd find a solely planet-industry-linked upgrade path to be even worse. Being able to do both wouldn't be too bad, though. Maybe drop the 10 or so constructors to make the functional part of the base instantly, then let the planet-based process fortify it.

Honestly, I'd be happier if we could put multiple special modules on a single hull. A cargo ship with 5 cargo modules that can be built on a reasonably productive planet is easier to manage than 5 planets building 5 tiny hulled constructors which then have to converge on the construction site. Mining modules, even more so - it took more than a game year to fully upgrade an asteroid mine up to full capacity. Getting 5 times the trade income from a single route would make trade more valuable on huge maps, too. GC2 trade often wasn't worth the investment to make good freighters. I doubt I was the only one that used bare tiny hulls to establish routes solely for the diplomatic benefits.