I think the promise of HC of the Future is not usually a good thing. Creates weird politics in the coaching ranks, players, etc... See Holmgren and Mora in Seattle a couple of years ago. That was a horrid disaster for that organization.
Best recommendation was ensure a super quality organization bent on winning a couple of super bowls and the hope that he wants to plant here for a bit and be a key part of that with a name your price option at the end of it. Or better yet he takes the Joe Collier approach and decides he wants to be a DC for the rest of his career.
Finally, what's to say that he would be a good HC here. He was not in Jacksonville. Lots of amazing coordinators or coaches who made really bad head coaches. Wade Phillips is a classic example as well as the aforementioned Collier.