Okay, as discussed on plurk, we've come up with this solution:

Will arrives with his chest - please add this to your inventory - and cannot be separated from his heart for more than a distance of "one day by foot" travel. If he goes beyond that limit he will become weak or ill, and compelled to return to the heart.

Awesome on the psychopomp, that works.

Once you add the chest to your inventory I can give you the go ahead.