My initial thoughts exactly, I think it may even be a completely different technology, more akin to an electro-staff, than the well known focusing crystal based weapon. It would also be cool if, like you say, was an ancient design, much like the Protosabers of 5,000 BBY.
On a side note, I've heard rumors (From the same people who predicted this trailers content almost frame for frame) That this "Dark Cyborg Man" is more of a Fanatic, than an actual Sith or trained force user, so maybe he just doesn't have the knowledge, skill and components to fashion a Lightsaber that works like the ones we know so well.
Either way, buzzing about this trailer! can't wait until Christmas 2015