Cool, best Superhero Rarity, she has her own cat and certainly enjoys liberating jewels from where they lay. Land rights, property boundaries, Psssft! Such mudane details are beyond someone as fabulous as Catmare.
Love the idea, but Catwoman is a DC creation, not Marvel as are Iron Man and Thor (well, he's a norse creation, but that's splitting hairs). If you want to stick to your Marvel theme, I suggest Black Cat. Other than this little rant from the fanboy in me, I love the drawings and hope you do more!
Batman is planned, though not for a pony that anyone has guessed so far, and it has no relation to Rarity at all. I tried to match up the ponies to their "best fit" and so none of them actually directly impact each other.
Someone did mention Spike as Batman, which totally would've worked if I hadn't sketched out my own choice already. I might still amend with a Batman!Spike if I feel like it though.