Interesting ideas. I’m a fan of cyberpunk Metropolis as well.
For Metallo though I think that military connection is key for a couple reasons.
1. It allows you to compare and contrast with Superman as an icon of “The American Way”. For all the patriotic associations, Superman has lines he won’t cross and stuff he refuses to do, despite what the government wants. TDKR turning him into a WMD is not supposed to be how he should be, but it makes for a fascinating exploration of the nature of patriotism. So use Metallo to explore that. He’s the military’s “Superman”, what they want Supes to be, a weapon they can aim and fire at will on their enemies.
2. It makes Metallo a more well rounded fleshed out character. He’s not just a psychotic criminal or a greedy underling, he’s a genuine patriot who believes that he’s doing what’s in the best interests of his country. That he gives body and soul to stop a perceived threat but is then basically cast aside once Supes and the govt reach an uneasy truce makes him all the more tragic, a way to be contemporary in how we treat soldiers without being too heavy handed imo.
3. When Metallo inevitably goes rogue after being treated like crap it puts Supes in a tough situation. If he can stop Corbyn what does he do with him then? If he just turns him over, the army isn’t going to just leave him in a cell. They’re absolutely going to try to use him to their own ends, so what does Clark do? How does he actually ensure justice when legally Corbyn belongs to the military? It’s an interesting conundrum.