What you do say is very true. I think your view is best, but, Louis is not going to be governor of Milan forever, and Henry just made his wife, at least in titles, superior to him. Governorship or not, this is something that is definetly going to rock the boat of French politics. Still - such a measure must be extremely unpopular within France's nobility. Brézé, if we can assume he is still similar to OTL Brézé, was extremely loyal to Francis and yet still Francis (Well Marie, but that's not who people are going to blame more likely) whored out his wife to England without Brézé's consent?
Some French drama would be cool. Francis and Marie have been super sucessful and I for one would like to see their reactions to having their boat rocket for once. An unhappy French nobility, fearing the same could be done to them, Brézé and his kin probably demanding compensation? Francis and Marie over-reacting and doing something stupid to either Brézé himself or his daughters? Marie claiming Brézé's daughter as maids, essentially against his will as hostages? All very interesting povs in my opinion.
Now the annulement if some drama happens is something I can see Henry jumping at. Although I don't personally see Diana supporting it - as much as I like her with Henry I doubt she would sacrifice the only "legal" chance she has to really ever see her daughters again. Unless Marie and Francis take poor Françoise and Louise as hostages, which.. probably won't go well.
This also leaves the question - this is bound to be a good spot for Charles to intervene in.
Aah I should stop rambling. Great timeline man!