Great manual !
I already wanted to this, but Googling already brought me to your walkthrough
I used a stock Raspberry Pi 3, with Raspbian Pixel edition for the setup.
Your manual covered almost everything
I had only to change 2 things to make it work :
1 API not available for Wio
Initially, I got an 404 error, when trying to access the API of a linked Wio device
To fix this I had to config the 000-default.conf file :
(see the deploy script from the wio site)
2 Automatically start server.py
After the installation, even after manually running server.py and installing the firmware, I still got an error when trying to automatically boot it.
To fix this, I had to make sure the Raspberry waited until it had network connection before booting.
This can be set in the GUI or using the shell command :
Boot Options/Wait for network at boot
Have fun !