As this post by Operation Sports' Chris Sanner shows, if Penn State in real life only offers 15 scholarships per year, it could be down to 50 to 55 scholarship athletes in two years anyway, because of losses to graduation, transferring, and leaving early.
Simulating through this, I'd suggest capping scholarship offers at 13 per year and, if you really want to be strict about it, 54 scholarship athletes on the roster, realizing that the latter may become moot by year three. A 54-man restriction may be problematic because I simulated a year in which I offered no scholarships, and the CPU added just six walk-ons to my roster, leaving me with a total of 58.
Plus, the game doesn't flag for you who is a walk-on and who is a scholarship athlete. So if you're going to manage the roster based on who has a scholarship and who doesn't, you'll need to write that down beside a player's name as soon as he's added to the roster.
• Ineligible for Big Ten title game until 2016: Simple solution: Make Penn State an independent school in the custom conferences menu before you start your career. If you only make this one change, the game will still largely preserve Penn State's Big Ten schedule (it swapped Iowa in week nine for Michigan for me, for some reason), they'll just be nonconference games. Now, with 11 schools, the Big Ten won't be staging a championship game, but this is still the fastest and easiest solution. When the four year ban is up, add Penn State back to the Big Ten. Conference alignments can be changed in the off-season of every year.
• Bowl ineligible until 2016: As said before, this can't be re-created. However, as an independent school, Penn State will get no benefit of Big Ten bowl ties. Its five-star prestige means a six-win season will probably still land the Nittany Lions somewhere, but it won't be anything that moves the needle for recruiting: Championship Contender, TV Exposure, etc.
• Forfeiture of all victories from 1998-2011: This actually has a minor manifestation in NCAA Football 13. The game tracks career coaching records, and four belong to "66-11 COACH (PSU)," aka the disgraced Joe Paterno. He's down for 409 career wins, 24 bowl victories and 37 bowl appearances, all of which were reduced significantly by vacating 13 years' worth of wins. To be notified you had broken one of these now outdated records would require, at minimum, 24 seasons in-game. If you've ever completed that many, congratulations.
Let's not forget the Nittany Lions will probably see players transfer out, as the NCAA has freed them to pursue a roster spot at another school without sacrificing a year of eligibility. So you may want to wait until just before the season starts to pick up some updated custom-named rosters, whose editors do a scrupulous job of dropping players who transfer out or get kicked off the team.