Would possibly be the most Epic Superhero Video Game Boss Battle ever.
I just came up with it. You fight both in the middle of Gotham Park. You fight off Harley and her gigantic Mallet-wielding skills as Ivy stands high above in a Venus Fly Trap shooting you (a la Arkham Asylum). Once you daze Harley, you can fling your batarangs at Ivy to dizzy her. The key is getting both of them dazed so you can use some awesome Bat-Gadget to take down Ivy's plants. And Harley gets progressively tougher as her agility makes it nearly impossible to land a punch without using Cape Stun or the Bat-Grapple.
Just my idea. What do you think? --- REAL Campers Camp with a Purpose. REAL Campers Camp for the Team.
God, that sounds brilliant. I hope something a lot like that makes it into the actual game. The Poison Ivy boss fight in Arkham Asylum was my favorite boss fight in the whole game, I'd love to revisit it, and Harley Quinn's addition would make it both funner and tougher. You, sir, are a genius.