I think you are really stretching it here.
The "Mary" in book 6 of Wars was hardly celebrating the eucharist- she roasted and ate her own son due to the desperate situations of the seige of Jerusalem by Titus.
As for names, there were relatively few Roman names, probably a lot more Greek, but to make a connection between a common name and the Flavian "roots" of Christianity is tenuous.
Josephus, certainly, was a sly fox and catered to the egos of Vespasian and all of his sons, to his great good fortune. He would not be above making up an oracle or prophecy to please them.
Interestingly, in Wars who is first through the breached walls of Jotapata? Why, General Titus!
And who was first through the breached walls of Gamala? Titus, of course!