The question the NRL needs to first ask is who is this event for? Is it to maximise viewership back here in Australia/NZ (and potentially UK)? Is it to try and showcase the sport to the US? Is it about the fans attending? Or something else?
Depending on who is the primary target will determine the number of teams and the structure. For example, if it's about TV audiences back in A/NZ then the two NRL games need to be at around that 7pm (2pm Sydney) & 9pm (4pm Sydney) time slots.
If they want to include Super League, the latest that game can be played is 1:30pm (9:30pm UK) to have any real impact back home, so to achieve those two goals, so you might as well put a Women's game in-between, cause otherwise there is too big of a gap.
If the aim is more about making it in the US, well then you want an NRL game kicking off sometime between 4pm-5pm local game (7pm-8pm ET), as it is prime time. But then you have to bring the other NRL game forward or you have to shove something else in-between (like they did this year).
If it's about those in Vegas, starting at 1pm and running 3 games back to back, so everything is wrapped up by 7pm local, is arguably the optimal. Night life in Vegas has a lot of competition, so making it easy for everyone to get to the NRL and then go to whatever shows, etc they may want to do.
If it's about showcasing the sport, then the earlier timeslots also work well in terms of getting maximum viewers and more likely being able to get coverage on FTA.
Reality is, the NRL can't have it all. They tried it this year, and as they saw it doesn't work. Even if the Jillaroos v England game was a thriller, most people aren't going to watch more than 3 games at a ground. Even with Magic, we see most fans watch just over 2 games.
It's a shame Vegas doesn't have a smaller, say 20K rectangular stadium, nearby. Then you could have say the Women's game being played on Friday night (Saturday afternoon back in Australia) as a lead in event.
