There's be few complaints if they signed Payton (at least until the team took the field, lol). However, I don't think that will happen, and Holmgren was lousy as a gm/hc. The Seahawks didn't have any success until they fired him as the gm. He might improve Romo's play, but he'd destroy the talent level around him.
This team needs a HC with good gm skills to succeed...and that's hard to find.