I actually featured a non-force sensitive Lightsaber Master in one of my campaigns- he was a Darth Vader "decoy". I decided that, since Lord Vader is such an obvious target for a rebel assassination squad (good luck to them, they'll need it), Vader had a small cadre (four, actually) of "fake Vaders", elite non-force using stormtroopers trained in advanced lightsaber combat techniques. As far as anyone else knew (other than vader and the emperor himself), these fake "vaders", unswervingly loyal to Lord Vader, were the real deal- and Vader used them to command troops and fleets in special engagements all over the galaxy. The one that the party confronted was a 12th level human Soldier with almost all his feats devoted to making him the ultimate lightsaber melee combatant.... let's just say they were utterly shocked when they found out that they had just defeated a fake dark lord of the sith...