Why?
The only thing slack does is prevents immediate reverse pressure (you have to take up the slack before the power generated at the cranks makes it to the back wheel). If you don't apply reverse force (ie, trackstanding or skidding, etc) slack doesn't ever factor into what your drivetrain does. the teeth and chain are always engaged, and it takes quite a bit of slack to risk dropping your chain.
with 1/2" or so of slack, you can still trackstand with no problems. try it for yourself. give yourself an inch of wiggle and go around the block. your bike won't explode, i promise.