Coach L we have used three basic bunt coverages for several years and have been very sucessfull with them. Of course it requires about 15 to 20 minutes each practice in order for us to be on top of our bunt-D game.
Bunt-1 Runner on first or no one on base. Third has line. Pitcher has middle. First has line. Ball bunted to pitcher first breaks back to first as soon as he sees its either right back to the pitcher or towards third just in case second is late covering. Ball is up first base line first takes it and second better be there.
Bunt-2 Runner on first and second or just second. Primary out is at third cant get third have to get him at first. First takes line. Pitcher takes line. Catcher takes middle. Third acts like hes coming but does not so we can either get the force at third or the tag. If the ball is bunted hard up the third base line the pitcher will never get there. Therefore we have third field anything hard up the line and give up third and get the out at first.
Bunt-3 Runner on second or runner on first and second and we have to get the out at third situation. Third plays in and has the line. Pitcher has the middle. First plays in and has the line. Short cheats towards third and breaks on the pitch towards third for the force or tag. Second fakes a break for second to act like a pick off play in order to freeze the runner at second. This allows the short stop to get to third in plenty of time ahead of the runner (hopefully).
Our bunt two is I think what you originally thinking about. It has worked well for us.