how about some and I mean ONLY SOME killstreaks.
no controllable choppers or anything
once you turn the power on you can send your coordinates and after a set amount of time your backup will arrive.
(a fuel remaining bar pops up for hovering killstreaks)
this could be:-
Airstrikes (normal & napalm)
basic chopper
harrier
early AC 130
And a heli that drops off backup help (but only last as long as u help them)
backup NPC characters like:-
Teams of snipers on roofs bringing plenty of backup fire from out the map.
(after some time you will hear the screems and zombie noises through your head set radio indicating they have died)
Teams using assault rifles dropped off by a chopper, they will attract all the zombies to them as long as u dont fire your guns.
(unless u watch them die, you will hear screems through your radio)
This could also be done with close range shotgun teams and Heavily armored LMG Teams (much like juggernauts but not as many as the other teams)
=D=D=D