On one hand I all for blacklisting ships I don't want to see appear in my fleets.
On the other though I don't want it to create extra player side tasks in keeping track of whether you have an adequate amount of fuel ships, cargo freighters etc.
it would be way more fun if there was a reason for it like say- you have to actually account for cost in that if you select only expensive ships youll get less, so you better select some of the cheaper ones or else your fleets will be too small
something like that would be a nice way to offset things given more player control would (theoretically) make things easier
and i mean really, for the players who think the game is too easy there are PLENTY of ways to make the game exponentially harder
Regarding this, while it's extra tasks on the player's side I could see this work. The question is, how? Do you get a base fleet cost (one for small, medium and large each) which increases depending on the number of player Heavy Industries, Orbital Works and Military Bases? Also, if you are swimming in cash, can you allocate some "defense budget" to it so that you are allowed to get bigger and better fleets?
This goes a bit far from the original topic though and doesn't really make up for the issue of e. g. seeing Gremlins in your fleets, while you have the Afflictor set up as preferred.
Alternative idea (that's how I do my playthroughs for a while now): Don't learn blueprints you don't want to use. Less fun, but effectively blocks all ships not learned.