As far as the blade, I would have to say not plasma, but an actual laser. i know what you are saying, "you can't stop a laser," well, yes you can. not yet, but scientists are working on making super-powerful electro-magnetic fields that can slow down lasers by an infinitesimal fraction of a second. eventually, if they continue work, they could actually be able to stop the laser. and maybe after that, be able to fit the necessary junk into a reasonably sized hilt.
as far as keeping track of the blade, the action of the laser burning through the air and making ozone may cause some resistance to simulate weight, but barring that, I would advise becoming powerful in kundalini meditation and making your psychic powers usable.
so, yeah, i think it is possible, and within a century, maybe sooner. well see