Both Urban and Dabo made the move from WR coach directly to HC. I'm sure there are others, but you're right it's not common. Honestly, I think the natural coaching progression of position coach to coordinator to head coach is overrated. There are a ton of guys out there who are fantastic game planners and play callers (coordinators) who make ****ty HCs, as well as position coaches who can be a great HCs without having to go through being a coordinator first. Coordinator and HC are completely different jobs, so I think it's funny that people so often believe someone absolutely has to be a coordinator first. It's a pretty archaic way of thinking, IMO, but it definitely happens.
Edit: Btw, I'm in no way advocating that Chev can/should make that jump (he's already going into year 2 in a coordinator role anyway).