Yeah, I think it would be a lot more interesting to keep him around as Sarge, espcially if he actually ended up on the team. Seeing them have to continue to deal with someone who likes Coulson but isn't, and seeing him have work under S.H.I.E.L.D.'s rules after about a century of doing his own thing, would be a lot more interesting than just reseting things back to how they were before this season.It would be a waste, a cheat, and a disservice to Clark Gregg if they just reset him to the old familiar Coulson rather than letting him and the writers continue to develop this new character and discover new facets to him.
If Sarge sticks around, I wonder if we might see at least one or two members of his team stick around too. I wouldn't mind if Snowflake and/or the big guy stuck around, I'm rather indifferent to Pax, so if someone were to go, he would be my choice.