The Brackenridge location would be a horrible location for an arena. Far from campus. Far from downtown. Far from mass transit. Think of all the parking garages they would have to build!
I still think the best location would be between 7th/8th street and Red River/Trinity. I know the massive Erwin Center would not fit on just two blocks but it seems possible that a newly designed arena could fit on the 275 ft * ~600 ft area created by closing Neches between 7th and 8th.
In Eugene, Oregon they wanted to build a new 16,000 seat arena on a two block site that is around 200 ft at it's narrowest width:
http://www.thefreelibrary.com/Thinki...ne.-a083122140
"A professor emeritus of landscape architecture at the UO, Rusch proposes building a new 16,000-seat basketball arena that would replace the venerable but cramped McArthur Court."
"In Rusch's vision, the new arena would be built on two blocks bordered by Broadway and East Eighth Avenue and by Hilyard and Ferry Streets."