Restricted by that fantasy, back to realism: Roger Goodell has already stated that L.A. likely would get two teams in an expansion to 34 teams. But 34 means 17 teams a conference which messes with schedules, and as others have noted there are multiple worthy towns -- San Antonio, Portland, Oklahoma City, Las Vegas, and Toronto come immediately and legitimately to mind -- who'd love to have and would rabidly support an NFL franchise.
I eliminate three of the five above and arrive at Portland and San Antonio as the likely 'realistic' additions. Don't think Dallas allows Oklahoma City in, Buffalo nixes Toronto, and the NFL blocks Las Vegas. San Antonio seems far enough away not to bother Dallas the way an OKC franchise would and, well, it's ridiculous that Texas doesn't have at least three teams considering how huge people are on football down there. And, uh, Portland has Paul Allen. Here's what NFL 36 looks like with Portland and San Antonio joining with the two LA teams (I've named the teams after famous folks associated with those cities):
*Teams in italics have switched conferences, but note that Cleveland was an NFC (actually NFL) team before the AFL-NFL merger.
(You can also see in the above a possible 34-team scenario, deleting Portland/SA so you have five teams in each of the West divisions and six in the other two.)
Below is a look at the good ol' days, the present day very symmetrical eight division set up. I actually wouldn't miss only having three divisional opponents, and would look forward to Bears-Colts and Bears-Browns twice a year (though that likely would be contingent on an 18-game regular season schedule):