Kenan Kong: The Superman of China. I think he could be a really interesting character to see in live action. I just kind of love his personality in the comics and I want to see him get more attention.
John Henry Irons: Steel. I love Steel, he’s one of my favorite DC Characters ever. Also his relationship with Lana Lang is fantastic and I’d like to see it happen in a later season.
Rocket Red. One of my favorite characters from the JLI. He’d be interesting to see, especially given current politics.
Seeing Lana as Superwoman would be pretty cool. Maybe she could get her powers like Superman Blue or something.
As @Zach11381 suggested I think Lobo would be a pretty cool recurring villain/anti-hero. Honestly I’d be fine if it was the same one from Krypton.
@DrakeWayne2248 suggested a return of Livewire and that sounds pretty awesome! I’d like a wardrobe update though.