So the manufacturer provides training and certification to local repair shops for their brand.
Good luck with that. Easier said than done. I have done mechanic work, still do a little on the side every now & then.
Good mechanics are hard to find, and the technology is constantly changing. Training is a constant issue. The 'shade tree' mechanic has long been a thing of the past.
Plus, there is the constant of buying tools, computer software and upgrading of facilities.
The manufactures love to cut hours paid for warranty work. Believe me, this will disincentivize shops wanting to deal with the manufactures.
Go to any sizeable dealership, thier parking lots are full and many of them have backlogs for weeks.
A mechanic shop is very capital intensive, and labor intensive. A good technician can make $100K a year.
Then you have the logistics of replacement parts. So are the manufactures going to ship in replacement parts from a central location? Or from distrubtion centers?
You still are going to run into a lot of the challenges of a local dealership.
Easier said than done.