If the average NFL coach wasn't so crappy, you might have a point. There already is a finger on the scale. If you're not part of the good ol' boys club, it's extremely hard to get in.
Increasing diversity in organisations is an extremely hard thing to do fairly. Quotas, giving benefits to hiring less qualified candidates based on race, on field benefits for minority hires and things of that nature cause more harm than good.
The only semi-fair means of approaching the problems would include changing culture (dismantling the good ol' boys mentality), and creating programs that find good minority candidates and spend significant time and effort developing them. The idea is to create equality of opportunity, not equality of outcome.