I suggested Superman Blue because I want J'onn to be brought closer into the Superbooks. He’s already great on Supergirl, and I think he’s be a great friend to Clark, both in terms of power level and alien anxieties. If there can be several Green Lanterns and Captain Americas, let’s have J'onn be a Superman.
Ideally, he’d forego green alien appearance and just be a black man, but one step at a time.
Another idea is to merge Oan Manhunters with Martian ones, and have his near-god powerset be Oan in nature, and not indigenously Martian. His body can be shape shifting organic Nth metal, for instance.