He's supposed to be "more man than machine" now, but is it true? More to the point, is it possible?
Vader is certainly down a few body parts. He lost his right arm to Count Dooku and had his left arm plus both legs cut off by Obi-Wan. As luck would have it, this isn't necessarily a death sentence as your more important parts are all safely snuggled away in your head and torso. Given that lightsabers would probably instantly cauterize a wound, he wouldn't even have the chance to bleed out before they found him.
With just a few advancements in our current mind controlled prosthetics and exoskeleton technology, yes, it would be possible to get Anakin back on his, er, feet. There's evidence to suggest that Vader's spinal cord is also synthetic which would perhaps make the integration even easier.
It's also probably not quite true that Vader is more machine than man. If we're talking about relative volume it's probably no more than 50/50 and more likely closer to a third, but we'll give them the benefit of the doubt and assume this was metaphorical.
Of course, one of the less-plausible aspects of Mr. Vader would probably be his larynx-crushing Force tendencies, but if you want a science-y perspective, then there are those who think that The Force could be something to do with the ability to manipulate the as-yet theoretical graviton. Perhaps thats what midichlorians do...