Mechs could be practical as powered EVA suits built for construction and repair in very dangerous environments.
Instead of being amazing combat fighters, they could offer unique support.
Like boosting a ship's maneuverability and speed (effectively portable thrusters that can move from ship to ship as theneed arises).
Or repairing armor, a function otherwise impossible for standard crew in pitched battle.
And these effects should be limited, with the battle mechs having to return to the mother carrier to restock on fuel or armor paneling. Just like bombers, where restocking depletes fighter recovery time.
