That's definitely possible, you just have to meet the deadline. If you don't need a powerline, you could also consider a WiFi mesh system. This one, for example, costs very little but offers a lot for the money. There are two mesh routers, each with a 3-port Gbit switch, and the mesh system can be expanded with additional devices up to 10.
Xiaomi AX3000
The Devolo Magic 2 WiFi 6 Multiroom Kit basically consists of the Starter Kit, supplemented with a Magic 2 WiFi 6 extension. Digitec also replaced the extension with another model in my case. It is difficult to judge whether this causes problems or not. In any case, Digitec should not deliver goods that do not correspond to the order without asking.
Your question is not explicitly related to the Develo. For my part, the router is always connected to the mains, the Develo adapters are plugged into a socket and supplied with power. That's my view and that's how I have it at home, everything works like that!
Der Hersteller meint max 12.4W pro Gerät https://www.devolo.ch/fileadmin/Web-Content/DE/products/hnw/magic-2-wifi-6/documents/ch/dev_Productdatasheet_Magic2WiFi6_02_CH_de_screen.pdf
Unless the car also has WiFi 6, it shouldn't do any good. Something with more/larger antennas is more likely to help. WiFi 6 is faster, there are fewer conflicts with neighbouring networks and many devices at the same time run cleanly in parallel.
This is exactly what it is intended for, among other things.
Please note: If the circuits are connected to different fuses, the transmission can be very poor or even impossible.
There are so-called phase couplers, but my electrician didn't know what they were.