That sounds a lot like the logic behind choosing 8-11 over 7:30-10:30 when the FCC mandated the access rule. For one, more affiliates carried their network news at 7 than is the case now; second, 7:30 was the hardest timeslot to program demographically, it being rich with kids and older people who'd likely be in bed by 10:30. I have to believe, however, that with a 9-11 primetime all bets are off concerning program content since we'd be talking about an overwhelmingly 18-49 or 25-54 demographic, at least on the two coasts. And it might raise a question similar to one in the '70s, when there were complaints that 8-9 (ET/PT) had to be restricted to family-friendly programming, while the networks were free to program sex and (especially) violence from 8-9 (CT/MT).That’s an interesting thought. I could see affiliates finding the idea of hour long local newscasts at 7 PM followed by syndicated programs from 8-9 pm interesting and potentially more attractive than an extra hour of local news at 10 Pm.
However, I can think of one station group that would welcome the 7-8 period for local news: Gray Television. They're already doing it in Charlotte (although to be accurate it's not a traditional local newscast), Louisville, and Charleston, SC, as well as Nashville (6-7 CT), and would like to have all of their stations doing it. Gray would probably be ecstatic at the thought of 7 PM newscasts followed on many of their stations by "Wheel of Fortune," "Jeopardy!", or "ET" in the 8-9 hour.