Really good post overall but I wanted to comment on this specific part because, IMO, I think right now is probably one of the best times to be a dual-threat quarterback because of the actual or perceived success of several current NFL quarterbacks considered "dual-threat" (or, at the very least, more mobile and non-traditional pocket passers). Guys like Josh Allen, Jalen Hurts, Justin Fields, Patrick Mahomes, and Daniel Jones. Now, Jones and Fields aren't guys you'd willingly pick to lead your franchise if you could pick from several other NFL QBs, but they're still starters in the NFL.
So, I think in a vacuum, running a dual-threat QB in a college-specific offense isn't necessarily curtailing much. There are a lot of programs around the country that have done this and produced all-conference QB's or even an NFL QB... teams which, on paper, have less recruited talent than Nebraska. I think the bigger problem is Nebraska can't sustain success and can't develop a QB. If I'm a good high school QB, I would have a very hard time choosing Nebraska over frankly 40-50 other programs that have at least shown me something interesting the last near decade.