Hmm... Well, shouldn't it still be possible though? Because, when you think about it, if the double bladed sabers use on set of crystals, there's just something that isn't blocking the crystal flow on the other side that IS there in regular sabers. So, in theory, couldn't a button or something just shift in a block?
I'm not one of those people that really builds up knowledge on how sabers are built, so I really don't know for sure, this is just kind of me theorizing.