My idea is slightly different.
McCourty at starting S. Ryan at S on passing packages. Harmon as S on rushing packages. McCourty getting a blow every now and then on rushing packages with Ryan in.
We got our outside CB's, our slot, and a good back-up CB in Dennard in this configuration - good enough we can take the starters off the field every now and then to stay fresh.
A young ball hawking CB with some holes in his game at CB might make an excellent S.
If that's the plan, forget drafting a S high. Back to DE, DT, TE, OT as the candidates.