Impossible to know if he'll be successful in the SEC; there's nothing on which to base that prediction.
But, as was noted above, the thread is asking the grade of the hire, not the coach.
As such, if your 1st choice is an A, your 2nd is a B, 3rd is a C, and so on, then Jones likely falls into the D range.
However, even that grade says absolutely nothing about whether or not he'll be a great coach at UT; only time will determine that.
The hiring of Spurrier, Saban, Miles, Meyer, and Muschamp didn't scare anybody in the SEC either... at first.