HIGHLY doubt you'd get Cowher out of retirement now. No on Billick and I think Marty is done with the NFL
Only guys on your offensive list I'd look at are Carmichael the Grudens and Roman. Kevin Gilbride is close to retirement and the others have proven to be just meh as head coaches.
Some good defensive guys there, but probably wouldn't go with Dan Pees. Not thrilled with the idea of the Tampa 2 but I think we got personnel for Lovie's D.
I'll throw out a few more names...
Darrell Bevell OC, Seattle
Jedd Fisch OC, Jacksonville (not good results yet, but I think he's a good coach)
Kyle Shanahan OC, Washington
Dave Toub ST Coach, Chicago
Mel Tucker DC, Chicago