I'd love Fenway's idea of a 4 PM game, as would most of the east coast. There would be so many good things about it, especially if they're playing a local EC team:
1) Gives a nice jet-lag bridge to the team. Starting a road trip with a Vegas game at 4 PM, and then playing the next game against Arizona, Colorado, or doing the California trip, with games at 7 PM local, would be just about as close to ideal as you could get.
2) Gives fans in the East a chance to watch a game without coming to work with a sleep hangover. (Or an actual hangover - I'm a Bruins fan, so I've been drinkin'...)
3) Gives local Vegas workers a chance to see the team. I have no idea if having a game get out at around 7 would be reasonable for casino workers. I've got a cousin who's a cop, and his shifts went from midnight-8, 8-4, or 4-midnight. But I imagine casinos are way more flexible, and maybe they have 8 PM - (3 +/- 1) AM shifts. Are casinos busy at 6? Do they need workers there before 7? Heck, you could schedule a 2 PM or 3 PM game if that's the case.
As far asa midnight game, that might be cute, but....nah.