Manchin wants to feel important, so if they gave him a few higher profile jobs, praised him for the performance thereof, and otherwise massaged his ego; I think he'd (1) agree to run for another term, and (2) go along with a few bigger picture things.
West Virginia is actually ideal for "hemp as biofuel" production; allocate some money, put Manchin "in charge", and he's the "hero" who brought a few thousand jobs for the cultivation, refining, and transportation that produces a few 100k bbls of diesel and biogas fueling the SE.
Manchin isn't an idiot, he just wants to feel important and on top of something. In a split Senate, he sees himself as "kingmaker". So give him something else to do.
**Sorry for the delay in this follow up, I'm at work and it moves in waves