What I'd like to see
1. WW2 in North Africa, the massive hero vs. tank battles. Also in Europe, D-Day etc. The massive hero vs. hero battles of the pacific, Captain Volcano vs. The Lord of Frosts. The Storm Korps, Fighting in Russia and the Soviet Defenders of the Motherland. just to name general ideas.
2. And one no ones mentioned, The Cold War and the clandestine metahuman fights in the USSR, South America, and Asia.
3. Something the Paragon City back story skips entirely (from the entirety that I've read atleast), The Vietnam War. No doubt there could be something the communists did that caused the U.S. and their heroes to fail. Who knows, it says secret supersoldier battles were common, maybe there's something they're not telling us? Maintaining secrecy and eliminating incriminating evidence was a common practice during the cold war.
just a few thoughts