I think your absolutely right and I don't know the solution. I don't think the issue at this point necessarily revolves around how to keep the players separate from the fans. I think the bigger question is without the proper means of testing in place how do you separate the players from essentially everyone who isn't part of the program. Like everyone else, everyone they come into contact with could be a carrier and they could unknowingly be spreading the virus.
It goes far beyond just the fans. The football players are interacting with coaches, trainers, cafeteria staff, other students (assuming school is back in session) officials, media, etc... all or most of which will not be quarantined. These individuals would most likely have family members as well as other individuals they interact with daily. I simply don't see how you put an athlete in a position in which they aren't exposed to the virus.
Cincinnati unexpectedly discontinued it's men's soccer program yesterday. I know very few care about soccer on here, but its also a fall sport. Their AD stating "widespread uncertainty and budget implications of supporting the number of student athletes at UC" as the primary reason. I think this is just another result of the fears that there's no model in place and no certainty as to how long the revenue sports will be out of commission.