That's all well and good, but then you're going to have to go out and find a solid-or-better safety to go with that OT, OG, or Pass Rusher. If you spend $3M on a safety who's a downgrade on Rhodes, are you really better with an average guard or below-average OT or OLB for $4M?
You're not going to get a starting-quality offensive tackle or rush linebacker for $4M, and you're likely not going to get a Pro-Bowl-Caliber safety for $3M.
IMO Safeties are a dime a dozen. I'd just as soon throw a cheap vet or a 3rd round rookie back there and spend money on a position that is harder to fill.