Yossarian wrote:
. . . the heroes did not much overlap, and when they did it was within editorial universes. . .

One tiny exception was in a Wonder Woman story. Diana Prince is again frustrated when Steve Trevor refuses to notice her. Queen Hipolyta tells her the tale of ancient Greece, when she had a secret identity as a common Amazon soldier (never mentioned before, and never since). Hercules only had eyes for the Amazon queen, while ignoring her other identity. Eventually, Hercules was temporarily put off by Hipolyta's indifference and decided to go slumming with the drab Amazon soldier, only to find her in the company of a handsome, young Greek officer, and getting a turn-down. The mighty Hercules -- kicked to the curb!

Taking her mother's example, Wonder Woman is ready after she rebuffs Steve yet again, and he decides to lower himself to ask out Diana Prince. In the final panel of the story, the Navy Lieutenant tells Trevor to take a hike as she walks away arm-in-arm with Superman!

Yossarian wrote:
I will re-read the Hawkman and Aquaman team up as part of my enjoyment of this month's Time Capsule goodness.

I will too. I haven't read it in at least four decades, when I was highly disappointed by it back then (unless I reread it when it was reprinted in the faux Brave-and-Bold Annual a few years ago -- it really was forgettable).

“Since Superman and Batman---and the newly formed team of J’onn J’onzz and Green Arrow---are away from Earth at this time, I need not concern myself with them just now!” I seem to remember thinking that this referred to the B&B team-up, without any further implications. The Commander's conjectures about it are fascinating.