don’t knock 80’s technology it was super cool 
I do think however to support this mode, it does have to come with the obligatory modem bleep sounds, so we can all reminisce in its glory. (perhaps) slightly more seriously, the main issue is speed, if you do this, downloading large ‘tapes’, will also transport you back to the 80’s, and reading a book whilst you wait for the download.
but id agree given its slow, and needs careful client setup, its not really that convenient (unlike usb networking via rndis, which is super useful imo).
anyway, just mentioned it as possible, in the rare case, that ‘its all you have’.
if you want a one wire (power+networking) solution, and/or closed wired network, I think probably power over ethernet with splitters, though admittedly the dongles are a bit of a pain in the neck.