Let me preface this by saying I fully understand the differences in the two time periods. HOWEVER...

If some late-Republican or early-Imperial bad ass legions showed up just before the Battle of Adrianople, could they have turned the tide? Not necessarily the number of men. I'm thinking more about the quality of their training, their armor, and their aire of invincibility they had from conquering so much without too much effort.

I just think about Caesar's men showing up and facing down the heaviest charging horses and just holding the line, knowing they would come out on top because heavy, disciplined infantry can take the heaviest of cavalry charges head on. I'm not a huge scholar of battle history though. More generally a lover of all areas of Roman history.

Hopefully you enjoy the light hearted discussion!