1. The one thing that annoys me with WOWS battles are that opposing fleets are always the same with regards to type and number of vessels.
Could they not use a points system . Associate a value for each ship type, such as 1 for DD & Sub, 2 for CL , 3 for CA, 4 for BB & CV
Mulitiply this by the level of the ship (I to X) to create a ship point value.. Then generate two opposing fleets with a nearly matching total points
This could generate more interesting battles such as 4 x DD against 1 BB.
2. WOWS have done an excellent job on the design and play of subs and their interaction with destroyers and cruisers in the game. However I don't think subs would have normally been used as part of a fleet attacking another fleet. They sailed alone or came together as a wolf pack attacking single warships/merchant ships.
The most suitable scenario for them would be in attacking a convoy of merchant ships.
Using my suggested points system above, you could create two fleets. One of subs and the other of the other type of ships defending merchant ships in convoy.