If McElroy's ceiling in CP, so what?
If he shows to be a good player, great we have a QB. If he shows he is only a backup level QB, great, we spent a late 7th on a decent backup QB. That's great value at that place in the draft. And backup QB's are valuable. At least now he'll have some game experience. If he proves to be awful, well, not ideal, but then you know you need to bring in a new backup QB.
I think he'll be ok. But at least if he plays, we'll know. And if Sanchez does have anything left, maybe sitting a few weeks and watching will help him.