My preference is to open it up to anyone, since the prospect of having to start in D3 is, I suspect, a big deterrent to giving the game a try for a lot of prospective coaches. But either way, at least fix hiring to remove or drastically reduce the experience and success qualifications of all baseline C+ and lower programs (excepting all big 6 schools and a few high baseline mid-majors) so the most qualified human applicant gets the job. Keep the qualification requirements (though maybe loosen a little) for the higher baseline prestige programs.
If I was running WIS, I’d probably just turn D3 into a no-incentive, free-to-play sandbox for people who want to try the game out, experiment with some things, or just coach their alma mater. Then I’m fine with a separate pool of D3-only recruits.