He still would be a Junior eligible if the transfers to FBS with a redshit. Hes a senior eligible without the redshit
I wouldn't wish a redshit on anyone.
But seriously folks, if he transfers to FBS, he'd still have two years to play either way. Remember you get five to play four:
2017 - Played
2018 - Played or reshirted, doesn't matter with an FBS transfer
2019 - Mandatory sit-out
2020 - Eligible
2021 - Eligible
The 2017 redshirt only matters if he decides to stay or if he transfers down to FBS. In either case, a 2017 redshirt leaves him with three to play three.