One question to ask is, given the history of the existing 'unnecessary roughness' / 'illegal hit' rules (which have been around for decades), why haven't teams been incentivized to 'draw the foul' already? (in the nfl, faking an injury at critical times is already disincentivized, see http://static.nfl.com/static/content/public/image/rulebook/p... section 5 article 4 page 18)

Also given how much time is spent going over videos of games after the fact (at all levels from high school on up), someone trying to draw the foul stands a pretty good chance at being caught out at it, which opens them up to, say, getting a multi-game suspension.