Sure, the agents would have to figure out a way to pull him out of the gravitonium, and there’s still too much we don’t know about gravitonium to predict exactly how this would work, but it would be a killer way for S.H.I.E.L.D. to tie off a loose end and provide an answer to a major question regarding preventing the end of the world in Season 5.
As an academic expert on gravitonium who once was willing to do anything for what he saw as the greater good and who presumably has a greater understanding of the element after spending years suspended in it, Hall could be the perfect person to help the good guys figure out how to stop gravitonium from probably contributing to the destruction of the world.