Actually Wingman, began as more a Robin analog, was also retconed into being in the Batmen of All Nations / Club of Heroes. And later evolved into becoming more of a Batman analog.
Could be the Robin specific kept him out, yet I'm inclined to believe the Rajan Robin (actually "Rajah Rahbin" in story) was just so obscure even Morrison either missed or intentionally chose to skip him, because how obscure he was.
(How he got on MajorHoys radar? That is some deep diving into vintage lore)
Yet he really seems like just the type of character Morrison would have embraced into the Batmen of All Nations / Club of Heroes concept.
Maybe if a new creative team relaunches the Batmen of all Nations concept, they can re-work him in, and yeah, I think starting as a young Robin inspired analog, who as adult aspires to be a Batman analog, works fine. I would love the addition.