I think people are overlooking the qualifying statement that he's only suggesting this if the market for Charles or Peterson craters.
Because they've been missing in the draft and don't have guys to give extensions to the Hawks have unexpected cap room.
If the market for these guys crater you could get them without down the road cap commitments, and in that situation the Seahawks are a really attractive option for either of these guys because there aren't many teams that could give them a good chance to finally get a ring w/out any clear running backs in place (right now it's the Hawks, Pats, and maybe Packers depending on what happens with Lacy, although they seem pretty rightly happy with Montgomery).
For 4-5 million per with no back end commitments people really wouldn't rather have ADP active on game days over Alex Collins?
I see very little downside to it, save for the opportunity cost of that money going somewhere else (although again, the Hawks are unexpectedly finding themselves with a fair amount of cap room).