It's The Theater at Virgin Hotels Las Vegas. There isn't space for anything bigger.
The railings and stuff you see in the below picture are fixed. If they attempted to go with anything bigger then the first row of hard came fans would have been like 12 people
Here is the generic layout for a concert. The ring was in section FLR2. Everything behind that is the fixed seating (other than the couches) and railing area as you can see at the bottom of the above picture. Announcer's table and other ringing production/medical staff were in that area, which is what is directly behind seconds FLR1-FLR3 on the below diagram. If they would have gone with a bigger stage, then the bulk of the first row of hard cam attendees would have been the announcers and what not.
