This looks interesting.

[b]Would Supergirl be too much?[/b]
I imagine her as fairly new to earth, and her powers have yet to peek. However in many ways she would be the direct opposite of Batman. Great strength, yet limited skill. Awesome powers, but not much control over them. A bit childish and inexperienced, but wanting to do good.

Edit: Having a member of the team be all about power can also highlight one aspect: Simply punching harder than Bane is not enough, since his greatest power has always been his mind. Maybe Supergirl learns that the hard way.

[b]
If not, then I could do a Batwoman.[/b]
Already brooding. Having nightmares and PTSD from war. Having no problem with guns, in fact apart from her hand-to-hand combat that almost rivals Batman, she mixes in a bit of gunplay. However using guns also makes it that much harder not to kill. And since she has been at war and already kill, who knows ... why not kill again? Just with a cowl on this time. Hmm, sometimes it's tempting.