I would do 3 things:
1. Build a sideline/tunnel club and replace the embarrassment of a legacy tent. A true luxury experience can drive a lot of revenue. Access would be granted to anyone who has an east side club seat in the new stadium.
2. Suites. Club 22 pretty much paid for itself already. Imagine that x 50 or 60.
3. Build a designated tailgate space. Basically this just means developing a grass field with trees and a restroom facility or port a johns. Super cheap but if it's close to the stadium with grass and shade you could charge a few hundred bucks for a season pass to park there and generate a decent amount of cash.
All the excess cash flow would be more than enough for BYU to make the low interest loan payments back to themselves.