You can have first baseman stay back (some first baseman are put there because they don't move well, unfortunately, compared to others). Pitcher could field those bunts, but I worry about collisions with the baserunner.
If definitely depends on the abilities of the individual players. Having P cover bunts on the first base side is possible with a fast P and slow 1B. This simplifies the decision making process, since 1B covers first, 2B covers second, and SS covers third. With this approach, it will probably be necessary to bring in a relief pitcher in the middle of the game, since the opposing team will probably bunt towards first to wear the pitcher down. With two good pitchers, though, it could be a viable strategy.