In campaign mode vanilla submarines have their docking hatches below them useless due to lack of shuttles wandering around. I wander if there could be a way of utilizing them in campaign mode by giving alien ruins dockable docking hatches. Those hatches would supply specifically rewired vanilla submarines with power but docking to them for too long would eventually break alien docking hatches as well as humans are unable to fix them at all so power is not limitless. I do also wander if those alien ruins shouldn't have limited power as well just in case if people wouldn't like breakable alien docking hatches and doors.

Bonus tip: Nuclear reactor can be shutdown after docking to alien ruins since that would only consume fuel rods.