So far, I think that's it for this one.
Initial idea by solo included Robin earlier and cuckold tendencies, but inserting third bat-character would be comical in the wrong way. Plus it took more time to set him up.
After an outlining the thing, I had two endings pinned down. This one and having crazed Batman grabbing Harley as she deems it too dangerous and tries to escape. This one seemed better for progression.