I've seen a lot of discussion recently about the imbalance between smaller ships and larger ships, however, I think most of that discussion is in the context of very late game fleets. The implicit idea is that all ships should be viable in late game fleets. I feel like that is not necessarily required, as long as all ships are viable/useful for a significant portion of the campaign.
An alternative to altering the balance of very late game ship composition (which will tend to bigger/more powerful ships naturally), is to try and change the balance of progression so that the player spends more time playing with smaller ships, even if they end up retiring them after some time. I think ship availability is something that could be tweaked a lot to affect that. You could alter access to markets, prices, salvage drop rates etc. to try and slow down the progression towards the biggest ships. I like the fact that big ships feel like an upgrade/reward over smaller ships, and not just a slower/tankier alternative.
I'm not going to get into to super specific suggestions for changing this stuff to avoid bloating the post too much (I think I'm going to make a separate thread about salvaging because I have several issues with the current implementation), but IMO, the overabundance of easily acquirable ships (both from salvage and stores) means the player basically scales up their fleet at the same rate they gain money (which is coincidentally all the player does) meaning they scale up very quickly. The effect on fleet balance is that they don't spend that much time playing with small ships because they quickly gain access to better ships.
Another thought: maybe the addition of more content for the player to do (rather than just grind cash and get a bigger fleet) will slow down progression leading the player to spend more time playing with smaller ships.
Anyway, I'd love to hear if other people think this is a good way to alter fleet balance and other suggestions about what to change.