Yeah, thinking about it more, I would change to the following:
3 - UAV
4 - Counter-UAV
4 - Care Package <-still unsure about this, though. ac130/cg care packages can be complete game changers.
5 - Sentry Gun
5 - Precision Airstrike
6 - Predator Missile
7 - Attack Helicopter
8 - Stealth Bomber
8 - Emergency Airdrop
9 - Harrier Strike
9 - EMP
10 - Pave Low
12 - AC-130
15 - Chopper Gunner
25 - Tactical Nuke
With this, you can have that 'default' COD4 killstreak loadout of UAV/Air Strike/Helicopter, which I thought was completely balanced to begin with.
EMP's usefulness is still iffy. For placement at 15, it should disable enemy map/scopes, kill all air support (including friendly), and last 2 minutes. During those 2 minutes, no air support can be called in (only enemy). This probably isn't realistic, but it seems more balanced for a 15 killstreak.