@SuperbattleshipYamato Sticking with the hidden subs subject,I would give destroyers a high probability,say 5/6, of finding subs in the same sz and zero chance of finding subs in an adjacent sz.
Also to prevent cheating,I’d use sealed envelopes or a locked box to store the sheets that record locations and previous movements of hidden subs.
On the subject of penalties for taking too long,I have another game the has "Time Machine"cards which when played,allows 1 selected D6 roll by yourself or an opponent to be cancelled and re-rolled.Example I’m bombing a factory and my opponent rolls 1 with his AA .I play a Time Machine card that I got because he was slow on a previous turn.I make him re-roll his AA and discard my Time machine card.Yes ,he could again roll 1 and my bomber dies.