I just thought of this earlier today while watching the beginning of the Jim/Sam era on Ion.
Remember back in season three, the concept Melinda discovered with the little boy Michael which I believe Payne had called 'misplaced spirits'? Where when a soul possesses a living body but in the struggle for control the occupying spirit to which the body belongs is temporarily shoved out. Paul Eastman had also used this (unintentionally) with Tom Gordon allowing him to appear to Melinda to give her messages.
So I had the thought of why couldn't Melinda have found a willing spirit, maybe even Jim's brother Dan instead of crossing him over who could jump into Sam's body temporarily shoving Jim back out who would then once again be aware of who is he is. I suppose this would not do much for the situation but it could have given Melinda more hope while Jim appeared to be getting further and further from her within Sam. Jim could have told her: "Stay strong Mel, no matter what happens, what Sam says to try to push you away, to distance you don't submit to him. Keep trying, never stop trying! You know I am there, but I am buried and only you can find me. Whenever he gives you a piece of me, even the smallest thing like a simple piece of knowledge that's me reminding you 'I'm here, I'm finding my way out of the darkness, back to you.'. Every piece of me you find in him means you're doing something right".
I think it would have given a lot more hope to the concept. She needed more strength.