This works in fiction because the writer has so much power, but game systems have really struggled with this, because the rules are too 'real world' simulationist rather than comics simulationist.
This is an exceeding good point. Part of what makes a good comic book is challenging the protagonists in ways that enable everyone to contribute. Some serious thinking is required to make Superman and Batman work well together in a typical game. This is even more true of the golden age versions of these characters.
The bat plane is neat and all but superman is moving at superluminal speeds.
I like the idea of determination scaling inversely with power. It not only matches the comics (where Batman has a strong plot influence) but avoids Batman being meaningless. I believe the Doctor Who RPG had something similar to make a companion viable.