It depends on the sort of action they want. If Arnie gets beaten up by a Predator, it's silly to expect a woman to go toe-to-toe physically with a Predator. If that isn't an issue, then there's no reason you couldn't have a woman in the lead role.
Mind you, no matter how the woman wins, you'll get complaints from the guys who dig big glistening muscles (in a totally hetero way) whining that the Predator has been emasculated (once they look up the meaning of emasculated).