Len Kasper, Duane Kiper and Jon Sciambi would all be excellent choices IMO. Marty Brennamen and Vin Sculley did fantastic work on national telecasts back in the day, though I'm unsure as to the willingness of either to do this kind of work today. I think TBS' biggest problem is likely that many of the best broadcasters are under contract to ESPN, FOX, or are on local NFL assignments at this time of year.