Thought I’d create an entirely new thread for this topic, since this is the real issue being discussed in various places.
There was discussion of having a structure in addition to the Shipyard that would restrict the number of fleets that could be retained at any given planet.
I can see a general issue with this entire concept. What about during war time? You are likely to need to house fleets at an unoccupied system because of proximity to the battle area. In this case, the planet isn’t yours, so you do not have the ability to even have a structure built.
I think fleet upkeep is the best option. A cost, in credits, per ship or fleet, based on the flagship’s hull. So a scout’s upkeep is super cheap, versus the most expensive fleet being a fleet with a Dread as a flagship.