[okanat]

I think you're trying to force the init and service manager systemd side to do network things. Well those are more complex than the purely service manager side to handle and that's ultimately why you struggle.

All the extra complexity is the reason that systemd ships with its own network daemon systemd-networkd to handle that complexity separately. It sounds like you need a .netdev file to create your virtual interface. Also .device files are also handled by networkd. I use them on our embedded devices pretty successfully. Take a look (especially wlan type): https://www.freedesktop.org/software/systemd/man/latest/syst...