je joins la réponse de Wayne du forum Gamesquad, vraiment clair comme réponse et qui confirme la réponse également de Lionel :
QUESTION: ok but if FPF it's not allowed during DFPh, what is allowed ?
REPONSE : You may use it during your opponent's MPh, and only vs moving units. Once the MPh is over and the DFPh started, FPF is no longer allowed.
A8.31, 1st. A8.4, 4th.
QUESTION : can i use inherent FP during DFPh after use BAZ ?
REPONSE : Sure. The BAZ is not marked, so you may Final Fire with it (A8.4, 1st). That uses up a SW capability of the squad. The possessing squad (marked First Fire) may then also Final Fire with its Inherent FP if otherwise able (A8.4, 3rd). After that, the stack (squad + BAZ) is marked Final Fire.