Norm Abram (This Old House) built and has plans for a shop table that has casters on the legs so that he can "drop" them down in order to roll the table around easily or sort of pull them up so the table is stable when he is working on it. Perhaps there is something to this idea that you could use. Another thought, if you could build legs that were two pieced near the bottom, you could find a way to adjust them up and down maybe with bolts and wing nuts. Just a thought ......