I can imagine some drawbacks of the system shown by you. First, it has its own optics, and they will not be comparable to a real macro or reproduction lens with flat field correction. Second, most of these duplicators were meant to be used with 35 mm film camera's, so they won't give you full frame coverage on a crop sensor. Thirdly, every second or 3d slide must be placed into the holder, necessitating refocusing with every second or 3d shot. I don't think they'll outperform a slide projector which you can buy for some € 30,- on the net.
Don't know of any duplicators meant to be placed before the camera's own optics, but in view of the camera lense's optical properties and minimum focusing distance I am rather sure that image quality won't be stellar - to say the least. To arrive at a 1:1 reproduction you would need either a strong diopter or large distancer in front of your lens or some tubes between your camera body and lens - and neither are helpful to image quality, set-up stability or reproduction reliability.
As far as synchronising slide advancement and exposure are concerned - they are not an issue. You use the remote control of the projector to advance each slide, and with the camera remote you activate the shutter for each subsequent slide. You can either control focus of each slide on your camera screen or trust that each slide will have the same focus distance of the former one - a high aperture count (f/16 e.g.) will help in this case.
I'm still looking for time and opportunity to try this out on my ca. 6.000 analog slides - I'd probably mount my Kiron 105/2.8 macro lens on my X-E1 body, put it on aperture priority, use my Orion slide projectors' remote to advance my slides and a traditional screw-in remote to activate my X-E1 shutter. I'd regularly check focus using the manual focus enlargement option on the center of the slide, since this will show the largest displacement under influence of the projectors lamp heat. The procedure is clear - now to find the time to translate it into action.