If I had my way then manufacturing would be publicly owned and based on open source principles

You start off very well... but after that sentence you just take a running nosedive into bog-standard green capitalist apologia.

They’re incredibly versatile and ~~hugely~~ somewhat efficient in ~~certain usecase~~ extremely limited situations,

FTFY.

Ecologically they can make a lot of sense too

No. They absolutely fucking do not in any way, shape or form.

aviation thus making flying a far less polluting means of travel than trains

Never going to happen, genius. Just the massive infrastructure air travel requires makes this attempt of yours a joke. When it comes to efficiency, nothing beats trains - except ships. That's not going to change any time soon - or possibly ever.