OG Captain America Buff Idea
I know we all wish Cap was more useful. His block proficiency is great... but that's about it. I think the way to make him useful (without changing the game dynamic in the early quests) is to make him a synergy/prefight god.
Start with him as a leader. Give him the ability to assign prefight abilities to a specific teammate (similar to Odin).
He could give perfect block chance, or the ability to block unblockable attacks, or stun resistance.
Other ideas could include giving a teammate a preflight assignment (like how Hercules gains feats). Once that teammate completes the assignment, they get a certain indefinite buff for that fight.
This way, he would be a huge asset on quests and wars, without changing his mechanics for when the AI plays him.