I totally might write this. There's a lot of fun elements to play with (fantasy vs. reality, Harley's increased strength, personality change, etc.). I've also
written a Harley story before, and have been itching to play a little more with that character.
No time frame, because I stay pretty busy, but I like the idea.
***edit***
Sorry! I didn't notice your post above indicating you planned to write it. In that case, yes, I'd recommend using that as an outline, slowing the pacing, and taking the time to expand on the idea.