The "Power down" concept is excellent, not least because it gives the game's interminable nebulas and asteroid fields a purpose in combat, as both refuges and possible pirate abodes. I can see this having great utillity in the boarder 'n' edge worlds especially, maybe having a ring of powered down ships just out of sight around a jump hole, waiting for the hostile (imagine Nomad/Core/Order wars with this).
It would give a degree of ambush functionality to all ship classes (I agree with class-based charge/de-charge times), with the potential for it to work both positively or negatively. Imagine if a battletrader ran into a depowered Pirate? Interesting role reversal there.
This even works for fleet engagements. De-power a fleet in a nebula and they've vanished, ready to strike or run. However I think the Power-Down mode should also be supplemented by vastly decreased sensor efficiency in nebulas and asteroid fields; in somewhere like Omega 7 or Sigma 13 you should really get zero sensor readout, or the NY badlands or the Edge nebula. That'd benefit everyone.
