Desire 1. The speed of your submarine should affect hydrophone detection range of enemies and yours. Cavitation should also be a thing making you easier to detect and have a harder time detecting others depending on how fast you are moving and how deep you are.
Desire 2. Significantly nerf torpedo range, buff reload speed. I dont like the idea of being an underwater sniping torpedo turret.
Desire 3. Make the torpedo angle fixed requiring you to rotate your sub to aim, dolphin attacks are annoying.
Despite 4. Battery charging underwater should be slower then above water and only happen when motionless at periscope depth, allow underwater charging to full battery, the faster you move underwater should drain battery.
Desire 5. Consider other people's suggestions as well I like some of them alot.