I understand we're discussing opinions, but I have a hard time envisioning the need for a huge university to have a need for "leverage" over a high school recruit. Just stikes be as unfair and "big brotherish".
I would have the AD call or maybe even visit in person with each LOI signed recruit and tell them UT will grant their release, but ask them to please wait 2 weeks or so to give the new staff a chance to meet them and build a relationship. If at that time they no longer feel its a good fit then certainly UT will honor their request for a release?