The Kilo is so stealthy, ironically, because it's a refinement of an old technology instead of a new tech. Diesel subs are, I think, one of the big concerns of the US Navy because they can sit motionless on battery power for days. Figure out which route a carrier group is taking because of a spy or something, and that could be problematic.
The more modern nuclear subs are generating some noise all the time because the reactor has to move water around and run turbines and stuff. A modern nuke is quieter than an old diesel, and the achilles heel of the modern diesel is the limited battery life.
If there's a way to have a part-time nuclear generator... that could be handy for managing noise profile.
