maybe a tiny crew of ~10 people would be sufficient with current automation. 2-3 sonar technicians, 1 weapons officer, 1 commander, 2-3 engineers, 2-3 regular crew... who else is needed?It's not small enough to be unmanned. The technology to pilot an unmanned submarine has probably not been exhaustively experimented on a sub of that size. A loss due to an accident would be very expensive.
A german 206 has a range of 4500 km surfaced and 420 km submerged at equal size and crew of 22. If you remove 25% of the bunks, rations and life support, you can put in another battery bank or more diesel/LOX you might get up to 600 km submerged which would be tactically useful.