Just a remainder of heroes remain unexamined in this last installment of a look back at the DC Comics character of 1943 and what could have been done with them to boost their success.
Shining Knight. Always seeming more like a fantasy strip poorly married to the superhero genre, the Shining Knight needs more grounding. If you're going to keep the winged horse, then the Shining Knight needs a less gaudy outfit -- realistic armor instead of gold chain (the "shining" quality could be from his sword and/or shield) -- a day job (something in the government, like the Training within Industry service, teaching chivalry to common Joes), and a supporting cast of regular people. Even more than Captain America, Shining Knight could really play up the "fish out of water" angle, having to constantly find new ways to adjust his 6th century thinking to the 20th century.
Star-Spangled Kid. Sylvester needs some of the retconning he would later get, like actual powers instead of just being an athletic kid. I'd, first, specify that he's 14, so he's more of a young man than a kid. Then I'd have a weaker prototype of Starman's gravity rod wind up in Sylvester's hands, like Roy Thomas would later do with the character. Make his "sidekick" Stripsey a smarter inventor, like was done in the Stars and STRIPE series of the '90s, and have him build an exoskeleton that doubles his normal strength (just not as powerful as the armor the later series would give him). Like the rest of the Soldiers of Victory, give them government jobs -- in their cases, honorary positions in the Office of Civilian Defense.
Starman. James Robinson showed Starman had, er, star power in the 1990s and much of that could be reapplied to the original Starman. Keep Robinson's innovations of a well-developed cityscape to base his adventures in, a rogues gallery that interacts with him differently than just wanting to fight all the time, the interesting hobby of collecting, and a strong supporting cast -- but without all of Robinson's dark cynicism. Since the original Starman would not have previous incarnations to interact with, play up the scientist angle and give him a group of scientists to hang out with. Maybe he's still a genius, but he didn't invent the gravity rod all on his lonesome. He could also use a love interest.
Three Aces. From what I gather, this strip was not canceled for lack of quality, but because its creator unfortunately died while serving in WWII. The story of the American Volunteer Group, pilots "unofficially" aiding China against Japan during the War, is a story modern audiences could use reminding of. "Whistler" Will Saunders, "Gunner" Bill, and "Fog" Fortune could use a dash of humor, some recurring villains, and maybe some of their supporting cast and villains could use magic to make up for the lack of superpowers in this strip. It could be an all-grownups version of Terry and the Pirates.
Vigilante.The modern day cowboy should always have been cool enough to carry his own title. I would only change his sidekick Stuff's name to something less offensive, like maybe Song. Make Song an equal partner (and specify that he's 20 years old). Then I'd soup up his rogues gallery, give Vigilante a love interest, and a job in the U.S. Fish & Wildlife Service to help give him focus.
Whip. This one required an awful lot of thought. Substituting a whip for a sword doesn't make this any less of a Zorro clone and taking just a few elements away from the character barely conceals that. I think this is one character that is better served by a complete do-over. Keep the name, location (LA), and the weapon of choice, but make him a soldier of fortune/weapons master who has killed and is looking to redeem himself by acts of good.
Wildcat. One of those golden age heroes who seems more popular now than he ever was back in the day. I think what Wildcat was missing back then was more time out of uniform. In the '90s he was shown to be a personable and chummy guy. He should have a larger supporting cast to pal around with when not in costume.
Zatara. Get the man out of the tuxedo. He can wear fine suits, but he needs to look less like a Mandrake clone. His magic needs to be less than all-powerful, too. We need to see Zatara in danger. International intrigue would be nice. He has a recurring villainess, the Tigress, and that could be spiced up with more tension.