International Development Management is proposing a three venue trifecta of football, baseball and basketball/hockey arenas. Mainly to attract pro teams to Las Vegas.
"The $1.57 billion Las Vegas National Sports Center plan includes a proposal for a 17,500-seat arena for basketball and hockey, a 9,000-seat partially enclosed baseball stadium and a 50,000-seat partially enclosed football stadium. The baseball and football stadiums could be expanded to 36,000 and 75,000 seats, respectively, to host Major League Baseball and the National Football League"
The article by the Las Vegas Sun also mentions that they would lease rights to use the facilities for $1 per year.