When BB grooms coaches, he moves them around. It’s how he was brought up too. Not only w/in O or D roles, but also ST (you know he loves that).
the notable exceptions were Dante and Ivan Fears. Dante was always happy being what he was and reported publicly that he turned down outside promotion offers -I assume he turned down internal offers as well.
Troy started coaching in ST if I’m not mistaken and was working with some of the wr (at least as returners, but I think on wr stuff too) even if not a named er coach.
I wouldn’t be surprised if bb made him Ivan’s deputy for a year to learn the job (round out his coach skill set) or even maybe Ivan is retiring or gave bb a 1year out notice (to retire in 22).
Would hate to see fears retire/ depart for promotion, but change is perpetuall.