I've always been a little disappointed that nothing was ever done with J'onn and Blue and Gold. Yes, he's pretty much the father figure of their team but I never got the impression those two were that close to him. J'onn was furious with Ted for talking to tablods about Tora after she died which helped create Extreme Justice (see what you could have prevented J'onn?) There was also his last words to Ted that basically insulted and ignored him.
With Booster there's an odd bit of protectiveness and guilt. See, at the very last issue of the first BG series the heroes didn't believe Booster when he said he wasn't a traitor. The only reason they actually took him back was because Herald told J'onn that Booster was special and needed to stay in the past. Which J'onn takes to mean that Booster must never know the truth (yeah Extreme Justice has Booster and Ted knowing although they don't say how.) J'onn tiptoes around the issue to say they want Booster back and Booster doesn't really buy it until the others talk him into it.
In 52 J'onn builds a statue for Booster after his "death" lamenting that he couldn't face him after Ted died. Fire also mentions the two meeting to talk about Max before J'onn dismisses him angryly. I'd love to see J'onns' take of how Boosters' taken control of the JLI and really see the two talk. Plus interactions with Jaime would be welcomed. They came in contact once with the Titans but J'onn didn't stop to talk.