The team needs to identify Jost's role to him. If he is a centre, they tell him that, and he spends the entire summer working on faceoffs. If he starts winning draws I think he has all the tools to be a solid 3C. Offense included. I think it would be a big and unjustified demotion to Jost to start next year as the 4th line centre given his performance this year. Remember he ended the regular season as 1C (due to injury, but still).
The thing I am unsure about is whether 3C is best for him or the team. I can see it being fine, so I wouldn't hate it, but in my opinion I like him as our swiss-army knife that can move up/down the lineup and from W > C. I'd rather him 'slot in' as a bottom six or even middle-six winger (assuming we spread out our offense to three lines). Probably with some combination of actual centres Kadri/Newhook/Danault/UFA at centre, and if there is an injury Jost can cover it, rather than a guy like Compher, who was okay vs Vegas but seems to be much better at wing than at C. I think this would be a perfect role for Jost rather than just assigning him 3C (or 4C).