It would make sense to me, but it would not address the question of minimum sentence for, let's call it, commercial kidnapping. With a minimum sentence you're boxing in the judiciary, but you're also providing a motive for the kidnapper to perhaps act very viciously and do something to the child, so that he won't be identified. Then the minimum sentence becomes academic, because he doesn't think he's going to be caught.
I'm still a little concerned about a minimum sentence that's absolute. Cases are not all the same, as you know, and the minimum sentence may be inadequate in a number of circumstances of commercial kidnapping, but in other cases it may not be proper.