Re: Nothing but Squat
you would get stronger and faster.
if adding mass up top to slow you down is a concern, i would still recommend throwing pushups / dips and pullups / chins on a regular basis. you won't gain mass with these bodyweight exercises, but will still keep the muscles fit and functional and reasonably strong. i would also suggest adding a few sets of deadlifts, leg curls, glute ham, or power cleans after the squats to balance things out a little.