Lowe speaks muchas Truth.
And here's the biggest bite: He's male and old. The shaft would be so bad...
But don't look at it that way. Somehow Grandis just doesn't fit into things as much as Aurion did; Keroko was the Ace who wasn't not a Sue; Kha was the Ace who wasn't a girl; Aurion was the Ace who isn't a frontliner.
Each OC Ace just changed 1 part of the Ace formula, and has been there ever since. So Oji-chan is as much a part of the A Team as everyone else.