Of all the combat scenarios in the game, the one I find the most problematic is the retreat of "too large" fleets. If you want to retreat in a big fleet you have to fight until either
- you dealt significant damage to the enemy, which is often impossible when they far outnumber you, or
- you lose enough ships that you are not longer considered a large fleet.
But it is not indicated when this point is reached, so you might have to retreat multiple times (losing CR) to check if you are eligible already. In practice, this makes losing your entire fleet a far more likely thing than it has to be.
I gather that the main reason to limit retreat is performance related, because a big fleet can't be deployed all at once.
So, I'd suggest to at least better indicate when your fleet would be eligible for a retreat (a counter how many enemy/own ships have to be destroyed still?), or better, to come up with a new combat scenario for these types of situations.
My idea for such an scenario would be this:
When encountering an overwhelming enemy force, you select some of your fleet to fight a time-limited delaying action against the enemy. All your ships not part of that action will be in an autoresolved escape scenario. (Autoresolved, because then the size is not performance-limited.)
Int he delaying scenario, the enemy has the goal to send ships to the border on your side of the map as fast as possible. All enemy ships that reach that border within a time limit burn away and will be the pursuing force in the autoresolved escape scenario. Your goal is to stop the enemy ships from crossing your border, and thus increase the chances of your fleeing ships. When the timer ends, the remaining enemy ships can no longer join the pursuit. They will now likely destroy or root your delaying force, or if they are in turn defeated, the scenario will reset. At any point, you can retreat your delaying force and fight a standard escape scenario with them. At the end the survivors from the autoresolved escape scenario and the escape scenario of the delaying force will be joined again on the campaign map into one fleet.
Feel free to come up with a better scenario, I think there are many better options than what we have now!