Do you imagine pumping as crew activity as pushing pump button by mouse button or moving handwell to the top and back, again and again?
IMHO the better way is simulation of damage effects (especially that campaign is linear missions based):
Leaks: increase weight on sub, problems with trimming, speed, manoeuvering (higher inertia of sub), solved by noise pumping on.
No oxygen: screen is going to be darker and darker, solved by surfacing
Equipment malfunction: a simple brain-game to connect wires between point A and B.
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