If Tom Cable returns as head coach, the following players could be signed at reasonable prices and would fit in well in the zone blocking scheme (I'm not sure about Stacy Andrews though). All are currently unrestricted free agents and haven't been tagged yet or doubt they will be.
Centers: Matt Birk, Jeff Saturday, & Mike Goff
Tackles: Mark Tauscher & George Foster
Guards: Chris Gray, John Welbourn, Stacy Andrews
Cable isn't going to bring in big money lineman; he's going to bring in players that fit his system. If we signed Tauscher, Foster, Birk, and drafted a lineman we'd be pretty solid.
Drafting an offensive lineman with the first pick isn't worth it at this point. Most likely when we pick at No. 7, the best strategy will be to pick the best available player and that could be Michael Crabtree or Jeremy Maclin.