2 civilians, 2 police officers and 2 agents, if they don't die and you have brain v3 you can persuade anybody.
But dont forget to not persuade objectives supposed to be assasinated because you can't harm them after that, only police, guards and no-persuaded agents or some explosion. Also don't even try persuade objective who is supposed to act independently because after that is mission-breaking and all you need after that in worst case is withdrawn from mission by escape and restart it again.
If all cryo chambers are filled with crappy mods/equipment/agents and no place to new better ones you can make them killed in action.
I see is hardest to accquire female agents as most of them are always male, 75% world map completed and I still have only Bush, Jones, Snelling as female. I try if possible to capture that female agent in Yukon as I wanted team of terminatrixes from beginning. ;-)
EDIT. Pffft, just got male Brazzier even though it was female agent...
Post edited December 21, 2012 by HenitoKisou