Thinking back before I picked up Batgirl, I had two other character ideas that caught my fancy.  One of them was Supergirl and the  other was She-Hulk.

I didn't waste too much time on the Supergirl idea since a really good character concept for her was quickly created but I remember I was split on the time between a Supergirl concept and a Power Girl concept.  In either case I would try to make the concept different enough from my fond memories so I don't feel too tied down by the character like Batgirl kind of did with me.

As for She-Hulk, at the time I was thinking just a version of the original but after thinking about it I just don't know enough about she-hulk to make a good one, but I know a good deal about Hulk.  So in a She-Hulk case I was thinking maybe twisting around the original Hulk story so that it is Betty Ross who gets transformed into the first Hulk rather than Bruce Banner.  Just thinking about the complications such a change would have on the entire story would make for a unique experience, especially with how Thunderbolt Ross would react to such a situation, having his own daughter transformed rather than some nasty scientist man who likes his daughter.