The Marines would have no motive to fight the Romans. They would have a motive to join the Romans and wipe out the Arabs.
That reminds me of another 'what-if?'.
What if Caesar (a friend of the Jews) had not been assassinated and had left for his invasion of Parthia (Iran) and consequently made a province of the Middle East? (He was scheduled to leave two days after the Ides of March)
No Roman sack of Jerusalem and no rise of Islam.....ever.
A man can dream, can't he?