Much of Rome's military strength came from it being much better organized then its neighbors and its army having better discipline and courage than its competitors. Your plan wouldn't counter these key advantages.

Plus, even with superior military tech you almost certainly would not be able to convince even a few barbarians to accept your leadership or probably even advice.

Arrive somewhere with good horses and poor leadership on the edge of the Roman Empire, implement Mongolian horsemanship/mobility/unit-tactics, most of which should be possible with the current day's technology in a horsemanship culture -

Is that true? Edward Luttwak in his book on Byzantine strategy remarks that the Mongol's reflex bows were very complex to make and hard to master - the Byzantine cataphracts had to constantly train just to keep their horse archery up to snuff.