Can you clarify what you mean by exit-set work? You are right about his size, but I think his skill and tenacity can make up for it. Longer term, I think I'd like him back at 6 when Foran retires (or is inevitably injured...) so 23/24 may be a learning period for both AJ and Sexton.
When the wingers and centres take hit ups coming out of your own half, when the team is pinned down on their own line. Even though Talakai hasn't been as dangerous in recent weeks his hitups to get the team out of trouble have been fantastic, it's hard to imagine AJ doing that at centre.