Those are some really good points, Robinson does tend to mine the past of his characters, and that was one of the more damning aspects to Diggle's run. I'd counter, though, with the notion that Diggle's continuity dredging wasn't what made his run so forgettable, it was that he regurgitated past minutia while simultaneously sacrificing character moments for plot mechanics. I don't think Robinson would do that, because in his better works like Scarlet Witch and especially Starman, he grounded the series in heavy character pieces while also laying down all of the plots for his endgame. Robinson would bring the character's heart and humanity back, instead of just sending him on neverending quests.
Or he'd write something like Justice League: Cry for Justice and make me look like a fucking idiot for suggesting him in the first place. It's a toss up.