At this scoring setting, it is a waste of a pick to bother drafting one, unless games in your league routinely end up 15-12.
We looked at this option as well, but were looking at the following rules:
1. Starting the COACH in the starting lineup would be optional week to week
2. If the COACH's NFL team wins his game, +10 points for the fantasy team
3. If the COACH's NFL team loses his game, -5 points for the fantasy team
4. double the fantasy points if a coach wins his game in OT.
The reason for the +10/-5 was to make the consideration about whether to draft one or more coaches a real decision, since you might pick up 100 points or so from a Bill Belichick during the course of a season.
With the +2/-2 setting, I wouldn't do anything more than just grab one off of waivers once in a while if I saw a matchup I really liked.