I am going to half-like the suggestion by wreckless.
I agree is rather strange that a carrier can be created out of thin air.
Something feels off to me about the shipyard requirement though.
Unless it was very low or constant cost, it could hurt some reasonable strategies.
For instance you couldn’t as easily send ships to a planet at the edge of your scanning in a dark galaxy, then craft a carrier, and send to two more planets in opposite directions. It also makes sending to a planet outside your scan range a bigger gamble. You don’t know if you will be able to build a carrier or not.
Lastly I feel it would just put more weight on the money strategy which already seems to be favored. (but that is a topic for a different thread)
Regardless, I do think it has potential to be a good optional feature.
Here’s a counter idea to address the idea of ships appearing from nowhere -
Have building a carrier subtract from your ship production the turn it happens. This way the ships are coming from somewhere at least, unless currency is actually carriers
There’s already lots of math around when planets build ships, add an extra chunk to that equation.
Each planets production per tick would be [Current Calculation] - [ Carriers Built * Planet Industry / Total Industry]
Not knowing the source code, I don’t know how complicated that actually is. I structured the equation that way since it allows the feature to be optional and hopefully doesn’t require directly changing the existing back end math.
Sorry for the long babble!