It hasn't been said or discussed to my knowledge, and it's a fair point, but I don't think Fujitora will simply stand aside. More importantly, Fujitora isn't very happy about Doflamingo going over the Marines' heads, and him hearing Caesar (the wanted mad scientist) refer to Doflamingo as Joker is definitely going to complicate matters. Doflamingo meant to kill Smoker and his crew for learning he was Joker, after all. Edit: pulled RobinotX's image for reference.
Since there was no way I could keep up with this thread to see if anyone else had proposed that idea I figured I should put that disclaimer. You know I actually missed that panel you posted, thanks for pointing it out.
Fujitora definitely isn't happy with the situation and to add on the fact that he may now be aware of Joker's true identity, really could change up Donflamingo's expectations in this situation. While he may not openly oppose him, Fujitora is under no obligation to go along with Donflamingo's plans.