Interesting. I suppose there are a percentage of players that this may work against, but then again, with those players you could probably just smash the rack open, call one of the balls somewhere, and just let them run their 5 or 6 balls. 
It's a move I suppose, but if you consider the percentage of players who may fall for this, vs the percentage of better position you would come away with using either what Mully suggests, or even playing the shot and getting into a good position to play a standard safety, I'd choose one of the latter options.
In any kind of defensive situation like this that I'm left with it is automatically programed in my head to simply take the scratch, roll the cue ball off the bottom rail into the balls lightly and knock a ball or two loose above the rack. Let my opponent play safe or scratch and then take if from there.

It's a move I suppose, but if you consider the percentage of players who may fall for this, vs the percentage of better position you would come away with using either what Mully suggests, or even playing the shot and getting into a good position to play a standard safety, I'd choose one of the latter options.
In any kind of defensive situation like this that I'm left with it is automatically programed in my head to simply take the scratch, roll the cue ball off the bottom rail into the balls lightly and knock a ball or two loose above the rack. Let my opponent play safe or scratch and then take if from there.