I just like to point out this one again:
any advice for a beginner in general?
Yes. Start simple.
Polyphonic octaves used to be out of DIY reality some time ago, unless you use a hexaphonic pickup with one octaver per string, and that probably won't even sound good. Now it is more affordable with the FV-1. Will it sound awesome? Maybe. Will it require a complex circuit to make it sound as good as possible? Sure. Is it a beginner project? Probably not.
If you're gonna use a pedal just to take it apart and put it inside another box, it makes more sense to just use it as another extra stompbox or to fully remove it from your project. You already have plenty of stuff to cover with "just" the rangemaster and the rat, like how to pick a transistor and properly bias it for the rangemaster, the reason of the ic you chose for the rat, diode clippers, hard clip vs soft clip, circuit troubleshooting... and, if you want to make your own boards (which isn't a hard deal for those projects even for a complete beginner), you can also include perfboard vs veroboard vs pcb, pcb tone transfer and etching (if you use pcb), layout drawing, and even more. And 12 weeks may be a good deadline or a very short one, it depends on the skills/knowledge you already have, what you still need to learn, and you'll need time to build it, troubleshoot it if needed, and do the paperwork.
Imo, if you pick just one of those circuits, build it all by yourself and document it very well, you'll end with a very good project and way simpler than your first idea. Kits will surely make it easier, but making the board by yourself may add a few satisfaction points when you finish it. Or may add a bit angry points if the board doesn't work

A nice document on the rangemaster:
http://www.geofex.com/article_folders/rangemaster/atboost.pdfA nice document on the rat:
https://www.electrosmash.com/proco-rat