I currently have an E39 530D M-Sport wagon. Yeah it's a diesel but damn it moves, total sleeper, plus wagon. Impressed with this M5 would be a massive understatement. Props for putting Euro spec head and tail lights on it amongst everything else.
Good luck trying to buy, let alone find an Evo IX wagon in the first. Saw a real live one about 10 years ago. Owner said he'd never sell it despite people asking him on a daily basis if he's interested in selling it.
The bashing your TRP or Box derailleur on a rock in New Zealand had me chuckling. As being from NZ, the irony is you could actually get the spares for it here. Other irony is, if it was mid-to-upper tier Shimano you might be outta luck. I had to wait 3 months for a Zee rear derailleur, and that was well before anything Covid-19. Then again the Shimano NZ is run by people who still think an MTB is just a BMX with gears therefore not important, and hardcore road cyclists.
Commencal have done it the interesting way for their 2021 bikes. Some (example Meta TR), are full Shimano and Fox, others are full Sram with Rock Shox.
Also see Microshift for their new wide range groupset. Reviews I've seen and read are pretty good. Kinda inclined to give their 10 speed wide range a go on a 1989 Rockhopper (insert lol comment).
Damn good read that was. Got me thinking even reevaluating my theories on custom build frame geometry. One question though about the Mudhugger guard on the rigid fork. Apart from the ties on the fork legs, did you have it connected to the forks arch and if so how?