Rick Insell has accomplished a lot at MTSU and IMO should be considered. I don't know if he would take the job as he has a good thing going at MTSU. I also don't know if he has the required personality to compete with the other SEC Head Coaches. However he should be able to build the program back to the levels that Jim Foster and Melanie Balcomb had where Vandy was going to the Tournament every year.
Rick Insell is 69 years old. It would surprise me a lot if Vandy were to go in that direction at this point, even though he is, as you say, a successful coach.