I know its impossible for them to be literally retractable, so what I'm suggesting is this: Make the vibroblade extend out from inside their gauntlet. The placement of this section of the Gauntlet is on top of the Gauntlet, not on the bottom like in Assassin's Creed, which is placed on the bottom. Similar to: Obviously on the upper left corner, but a lot longer, enough to make it like an actual blade, at least the size of a short lightsaber. On both arms if possible.