This is such a great project! Will follow for sure, same as I'm doing with that TAF from scratch thread.
I've been thinking about building my own MM from scratch over the last year and these "do it myself from scratch" thread's just increase my eagerness to get started If I do decide to actually start my crazy dream then I will buy a playfield and not make it myself though.
Been checking prices for needed parts and with most things added up it will be about the same (or even a bit more) than to buy an original working MM. The difference would be my pin having lots of parts being new and in great condition compared to a 25 year old worn game so might still be worth it, plus I will be having lots of fun while building it. Making the wire harness myself kind of scares me though haha.