I refinished two sets of W108 wood myself many years ago, and the results looked pretty good to my then untrained eye. Unfortunately, I sold both cars before I could determine the durability of the results. Since then, I've hung out at Drew's shop (Heritage Woodworks) enough so that I think I could now doo a much better job. It sounds like you're taking your time to do things carefully, and I'm sure the results will be excellent.
I have been planning to put together a set of wood for my W123 just for fun, using an exotic bubinga veneer I bought. It's pretty much love it or hate it, although the purists will most certainly wretch.