Hi,
If you check this link out
The guys at seaview did a long 2.4 km inspection
They also have a battery manager which allows the use of multiple battery’s.
If you go down the road of topside power. You will have to step the voltage up a lot for that length of tether or use bigger conductors which then leads to a larger tether and more drag. So more thruster Force is needed and so on.
Everything you have listed will work over fiber optics with the exception of the USBL which won’t work in a tunnel at that length anyway as there’s too much reflection from the tunnel.
I would say you would be better off with a cable counter on your tether so you know exactly how far down the tunnel you are.