That's a fascinating question and now I'm going down a rabbit hole. Sorry I don't recall the up-to-date names of all the venues.That's an interesting thought that I'm sure has pros and cons on either side. I wonder how many major cities in America would be able to make like 8 different basketball arenas in close proximity available for use at the same time. Indy seems potentially unique in that regard.
NYC could do it except no dome for the Final 4 (have the final 4 in Syracuse???). MSG, Barclay's, the Rock, new Islander's arena, Alumni Hall, the RAC, maybe even Hartford Civic Center, or Albany? Would be cool to have a NCAA tourney event in a historic arena like Rose Hill at Fordham but it's probably too small.
Other than NYC, I will skip any cities than don't have Dome Stadiums for the Final 4. I think most cities with Domes could probably handle it. Criteria was within a 2 hour drive of the host city. Not factoring in potential NBA/NHL schedule conflicts.
LA: new Rams stadium, Staples, the Forum (and then later what the Clippers plan to build). Pauley Pavilion, USC's arena, the Anaheim Pond, Pepperdine, UCSB, Long Beach State, and I'm sure others.
Houston: Texan's Stadium, Astros Stadium, Rockets, U of Houston, Texas A&M, Rice, UT-Austin.
Phoenix: Cardinals Stadium, Diamondbacks Stadium, Suns Arena, Hockey Arena, ASU, U of A,
DFW: JerryWorld, Mavericks arena, Texas Rangers new Stadium, TCU, SMU, Baylor
DETROIT: Ford Field, Red Wings/Pistons arena, UofM, Eastern Michigan, Oakland, Detroit Mercy,
ATLANTA: Mercedes Benz Dome, Hawks, GaTech, UGA, Georgia State, Auburn (AL), Chattanooga (TN)
New Orleans: SuperDome, Pelicans Arena, LSU, UNO, Tulane, Southern U, SE Louisiana U,
LAS VEGAS: The Death Star (Raiders Stadium), MGM Arena, Golden Knights Arena, Thomas & Mack, Orleans Arena, MSG Sphere (2023 - might not handle basketball),
MILWAUKEE: Miller Park (not sure if it could handle the Final 4), Bucks Arena, UW-Madison, UW-Green Bay, and you may be able to dip into Chicago for the early rounds.
TAMPA: Tropicana Field, USF, UCF, Orlando Magic, U of Florida, Disney arena(s)
MIAMI: Marlins Park (not sure it could handle Final 4), Heat Arena, Panthers Arena, U of M, Florida International, Florida Atlantic.