Only certain WRs can do this

This is why McVay has a "type".
They can't be one-trick ponies. They have to run a few routes well.
They also have to be disciplined and precise in their timing, or it falls apart. A Metcalf or a Pickens would never work.

But.... there is no reason why a team might not choose to go 3 LBs, but rather 3 CBs or and extra safety. But then, that's why they drafted Ferguson.

Still, Stafford has to be protected. So, the RB has to be a good pass pro, and so does the Oline.