Autoresolving sea battles is really lame and unfair cause autoresolve is a bit broken in the first place.
I'm not talking about actual RTS battles, cause with the current number of factions that would be a full blown game with its own dlc.
Rather something more realistic e.g.
Each faction can build at least 3 ship types that fight in auto resolve
Ships have some basic stats like ranged power, boarding power, accuracy, hp, boarding defense, maybe more
Auto resolve has 3 phases: long range combat, mid range combat, boarding. To make things bit more interesting you select a tactic for each phase which acts as a global modifier and can counter the enemy fleet + tactic (or not). Basically you and the AI blind pick a card with a modifier for each phase. There also can be weather modifiers on the map for more situational variance.
I didn't find the right solution from the Internet.