See, for myself I would only do that deal for Wentz. Of course no one knows who will be the better QB between Wentz and Goff, but my eye test says that Wentz has the higher ceiling. Goff is probably a less risky prospect. Cleveland "should" go with Goff. If they do then the Rams need to jump all over a trade like this.
JMO
I'd take Goff for that. The Rams want to cut Foles. Mason's Ram career is nearly over. While I'm not crazy about Goff's high end - getting a QB who should be decent or better in the NFL for a mid-first, a mid-second, and flotsam and jetsam is a bargain. I'd rather find a QB just at #15 - but it's a QB. If the Rams get a shot at a better prospect than is likely to fall to them for that price, they should do it.
But I doubt the Cowboys do it. Not impossible, though. Basically, that would be saying that Foles and Mason would be worth 300 points, a late 2nd round pick. That isn't insane, just not likely to be the case.