The easiest way for NDSU to move up is get a waiver like Liberty. Then find the P5 teams nearby who want to have 2 for 1 games, yearly schedule Mountain West and MAC. Scheduling will be really hard, might need to play 2 FCS teams every year. On the stadium front they can build an inflatable stadium for only $100-150 million that will seat 25-28k.
All this is a really hard sell for NDSU and Fargo. ESPN/ Fox will need to heavily support NDSU with $3-4 million a year for TV rights. It's a lot of hypotheticals, I just don't see it happening easily. Plus if NDSU has a P5/ G5 hybrid schedule it makes it very easy for coaches to get stolen. It takes one bad coach and everything goes off the rails. And then NDSU is no longer the ESPN darling.