To Rack'em et al: Most programs "take" four O-Line per year for fairly simple reasons. If you do, you will have about 16 total guys to work with, four of whom will be red-shirting/developing. That gives you 12 guys to form a comfortable two-deep [i.e. Ten players; none freshmen]. Ten decent "hits" at O-Line out of Twelve shots is a pretty high success rate and you might well not get it.
Run our own recent recruits through your reasoning here and see how comfortable you'd be after next year with "only" ZMartin, Watt, Lombard, NMartin, Nichols, Hegarty, Prestwood, Hanratty, Heggie, Carrico, and Decker, Harrell, and maybe no one else from this year's class to work with. SOME of those names look pretty good but few are proven at all. Remember that we want at least EIGHT of them to be able to play, as Kelly says, "Championship football". Some, frankly, DON't look too hot at the moment.
Elite programs would like to have more to work with to minimize risk-taking plus transfers plus injuries [a BIG deal with linemen] in this vital area. Stanley and someone like Armstead or Banner or several other possibilities would make this a lot more relaxed for the staff. We need to remember that players like Heggie and Carrico are late position shifters, and Nichols might be injury prone. Toss in a couple of "Cave" like tragedies and you're hurting where you can stand it the least.
People saying that Springman or Hounshell or Jarron Jones will "just move over" have no concept of what they are talking about. Becoming a good working-as-a-fivesome O-Lineman is not a weekend hobby. We need an abundance of elite personnel dedicated immediately to the tasks of the O-Line to be great there. I'm a broken record on this, but my brothers were all linemen, and they showed me what that took to be good at it.