It is possible, but would take a very long time and two (or more) crystals of the same size. So I would regiments two diffrent ones, but having one like that would certainly be more interesting. But these two crystals could interferer with your energy when changed, but probably not.
I wuld like to clarify that the crystals are all of similar size, and relatively small.
What I did was i took small glass rods and used a blow torch to heat the glass. I wrapped the glass around the handle to form the grip of the wand and with the glass that was hanging off the end i fashioned a loose cage that small crystals of any type can be pushed in and out of. It takes some delicate work to switch the crystals but thats how it works.