Scrag is talking about active sonar. Passive is another kettle of fish. His wish goes double for me in sonar range for surface ships! Seems like TM is way too sensitive on ASW detection right now. My life isn't in danger unless I'm stupid, but attacking an escorted convoy is a big problem.
But what I'd love to tinker with is three separate passive sonar heads, plus one active head using more real characteristics. Then I'd love to have this console to play with:

This is just one illustration from the
US Fleet Boat Sonar Manual. Not only did the different heads detect different frequencies of sound, but you had all kinds of filters and selective amplifiers to enhance what was detected to tease out the info you were interested in. I don't know about you, but that really blows my skirt up!
Of course there's no way for SH4. But this is a wish list. Maybe Ubi is wondering where to take their sub franchise and reads these things enough to pick up on our interest.