Just Fully restoring an existing pin (stripping down to Individ hardware pieces for cleaning and replacing) and stripping and redoing the cabinet with knowledge/experience working on pins is a huge task. There’s a reason not many people are attempting complete scratch builds of A list WPC’s..
I totally get wanting to take on a project, and the satisfaction of completing it. You’ve already delved in but I still echo a few others— start smaller or at least get a pin to familiarize with first. Manuals are great but it’s also not quite a factory how-to build this from ground up.. I love projects and have fully restored a classic WPC and in doing so I def. can say I’d never want to scratch build.. not to say u can’t do it but you’ll need to collect a lot of reference photos and there’s def. going to be irritation at times Sounds like you’re prepared for that though. Good luck!
Build a rotesserie for the Playfield - that’s a must.