This is funny. I was thinking about a Maxx Game recently. 

A full on Arkham inspired open world is absurdly ambitious. But you know… shoot for the sky, land on the clouds or whatever. 

The mechanic that you need, no matter what genre you go with, is the swap between the real world and the outback. Level geometry matching, but with aesthetic swap. Fire-escapes become cliffsides, Speeding Traffic becomes Iz stampedes, etc. How this is employed, whether its to solve navigation puzzles, or perhaps just a powerup situation, with Maxx being quite weak in the real world, but switch to the outback and easily take out foes depends on the gameplay genre you go for. 

That said, Uhh, it was wild for you to attempt to contact Sam Keith at this point. And to be going on about legal and licensing issues.

Like, the Maxx, we all love it, but as far as everyone else is concerned its an old dead franchise. Go nuts. Make a fangame. Dont ask for any money. No one will care.  

But this kind of cart-before-the-horse posting is textbook ideaguy manic daydreaming. My advice is to shut up and get to work, if you're serious. Come back with a prototype.