My white whale idea that likely won't come to pass, even with my admission that I'll probably try other characters, is still Carol Danvers, Green Lantern. One of y'all -- or a Hypester -- once just threw out the idea that Hal Jordan was Carol's wingman who perished on a mission, and so Carol's whole arc would be learning to overcome her fear and PTSD from that incident and becoming Green Lantern. It'd even explain how she could end up with NASA (taking a cushy desk job over anything remotely dangerous) and meeting Phillip Lawson aka Mar-Vell aka the Green Lantern of Sector 2814.
Pretty sure we talked about it when I did Tony Stark, Iron Lantern for Henry's first RPG Singular Universe thing. We had fun for a whole two or three posts but then Spider-Man become available because @Architect dropped off the face of the planet.