Would she work in Nolan's world?
Probably better than anyone else, although she'd require some revising. What with Neeson's character being a bit, well, dead (or so we must assume from the end of Batman Begins), she couldn't really be pushed into seducing Bruce Wayne by her father. But she could be looking for revenge for her dead dad and try to get to Wayne through his underpants. If she showed up in the third it would be a neat close to the trilogy (assuming Nolan directs a third and then stops). However, if the film were to have a shady love-interest lady, we'd rather it was Catwoman.

Who would we cast?
Someone who could be both bruised and steely, like Jennifer Connelly.