Isn't it possible to assign fantasy points to O-linemen based on how well the offense does? For example, since there are always 5 offensive linemen give each one 1/5 th of the total offensive yardage and/or 1/5 th of the points scored by the offense. then subtract points for sacks allowed, hurries allowed, things like that. You could give extra points if a lineman recovers a fumble, scores a TD, tackles a ball carrier after an interception or fumble recovery by the defense, etc.
I don't think we will ever see individual offensive linemen as a fantasy position. However, it should not be difficult to add a team OL position similar to the team defense position. I doubt we will see that anytime soon, though. Not enough demand.