Wait... what?
Well bring on the pants-in-briefcase routine.
(and will officers actually pull you over... for wearing pants?)

At first this seems good because its funny and hey "I would use the lane", but actually it would be very slightly bad. Not wearing pants is very easy, so basically everyone can use the lane. So it will be busy, just like any other lane. Thus there is no benefit to it. There is of course the disadvantage of the extra complication and enforcement, and the inconvenience at times when you must wear pants - you are basically just losing a lane. So overall, I think this would be bad, but only very slightly worse than normal.