Francis II died after falling from his horse in 1588 and only then Charles VIII forced Anne to marry him. I think that his accident could be butterflied, giving Francis some more years of life. If he is alive he would probably try to marry Anne to Maximilian or his son.
Whether Francis lives or dies as IOTL doesn't matter, in any case the Breton mentality is still that Anne needs to marry someone who can protect Breton Sovereignty, or whose father can protect Breton Sovereignty. No matter who ends up becoming Anne's future husband, short of the King of France himself, Charles VIII will not agree to the marriage, something he claimed the right to.
Anne of Brittany was betrothed to Edward Prince of Wales in 1483 (the future Edward V) - the key intention of the betrothal was to give her father protection from France and to give Brittany a semblance of independence once Anne inherited.
With Edward V's deposition and presumed murder and Francis of Brittany being drawn into the Duke of Orlean's conflict with the French regency - with her father's death and a fresh breton french conflict she was betrothed to Maximillian. When Max refused to come and rescue his bride she was formally betrothed to Charles VIII who repudiated the Archduchess Margaret of Austria in order to be free to marry Anne. At the time of the marriage she was just 14.
If Max was unwilling to fight for her for his own wife then I doubt he'd have risked a fresh conflict with France to secure her for his own second son.
I think you're confusing inability with unwillingness to fight. Maximilian was tied down in Hungary at the time of his marriage to Anne IOTL. Could he have left Hungary, I've hypothesized in All Hail Germania, that he could have without any real ill effect to his campaign in Hungary, but honestly I don't know enough about Hungarian History, and therefore assume that there was some reason why he felt that he had to stay. Francis' survival could very well butterfly away this situation, and then Maximilian would happily defend the Breton Inheritance and to get his daughter back since old Chuckie didn't want to be married to her anyways apparently.