I fail to see what is so confusing about my thinking. Any NBC affiliate manager in his/her right mind would want to run local news at 10/9 because of the potentially larger audiences and revenues. The only problem I could see would be on Saturdays if SNL were to move to 11/10 and, in the fall, a football game was still in progress. What time would SNL start? Sundays, I think NBC affiliates would gladly let NFL games run over so they could inherit their large audiences. Personally, I would be good with a 10 PM local newscast (after all, if I ran a station in the Central or Mountain time zones I'd have one anyway). And I don't give a rip what NBC does with Fallon.
It won't surprise me if, within the next decade or so, NBC is streaming the majority of its programming on Peacock, and all this is going to be a moot point. I am thoroughly convinced that, although I may not live to see it, daytime and prime time entertainment shows will go online just as the network radio shows of the '30s, '40s, and early '50s moved either to television or off the air altogether.