P4 teams only would work......or honestly, I'd just do B1G + SEC + ND/FSU/Clemson/Miami - 38 teams
And like with fantasy baseball having an innings cap, you could have a pass attempts cap at 500 or 600 or something for a season. So you only get points up to that ceiling.
It may take a step or two more than a log in and play NFL fantasy game, but it's completely doable.
The toughest part now is all the player movement. But that's not a dealbreaker.
And I don't think college football fandom is that far behind the NFL in terms of number of fans, it's just that so many people like both. And honestly, thanks to religion, people tend to do less errands on Sundays, so that means you're doing them on Saturday....during college football. So many wind up having more exposure and growing their allegiance more to NFL than college.
And if I could get any damn time freed up from producing orders of my WN game, I have so many versions I could create - so far, I only have normal, annual teams and all-time teams. I could do all-conference teams for each season, all-decade teams, all-decade conference teams, ect. All-American teams for each season....the list goes on and on.
The variety of college used to be magnificent. But it has already become so homogenous lately. The consolidation of conferences, the near uniformity of offenses (spread option), etc sucks. It's akin to the late 70s where everyone was running the wishbone, even hold-outs like Bear Bryant wound up running it. But thanks to BYU then Miami, the passing game started to spread and some diversity happened into the 90s. Still had option programs in the 90s, too. But then thanks to Meyer and RichRod, the shotgun spread option swept the country and I'm sitting here waiting for the next thing to get us out of this monotony.
Rant over, I guess.