Typically using bad starters in the rotation, even if they're young and cheap, doesn't help in building sustainable winners.
With that said, putting Sanchez in AAA as a starter would be the ideal situation. If AA's regime was still around, then I'd just stick him in the pen and not worry about it, but Atkins/Shapiro have a history of developing SP's. See if they can work some Cleveland SP magic on him in AAA. If not, then put him in the pen long-term. With his current skillset, he's a reliever. If they work on him and maybe help him develop a swing and miss pitch, then the chances of him becoming an MLB starter increase.