Every generation has its heroes and recalling them fondly and comparing them to one another is part of being a fan. However, I think it was/is a nice, but unwise, gesture to retire numbers. There are many other ways to honor a player's greatness including displaying jerseys, a ring of honor, etc. But, there are, obviously, a limited supply of numbers to serve an unlimited and, hopefully, endless number of great persons and players who either have played in the past or who will play for the Vols in the future.
I think UT should use "special" numbers in Vols' history to reward active players of achievement. UT should elevate being asked to wear a certain number to a special honor for a current player who is achieving greatness. But I don't think any number needs to be retired. The history of the exceptional players who wore a particular number in the past should be celebrated making the current wearer part of a continuing history of achievement.
Finally, I don't think any unproven recruit should ever get to demand a number regardless of talent. If that is the reason they use to decide where to go to school, that says a lot about the person involved. They won't be missed. Go Vols!