Yeah, 300km is not what it used to be on an ICE. A coolant/transmission flush and fill, plus some spark plugs. These will show up on an EV as well, minus the spark plugs, but you will spend way more on tires alone either way, so not something to worry about.

What you are describing is building individual power plants for DCFC stations. These would need engineering, land, and regular maintenance. Just because the fuel is cheaper does not mean that they are cheaper. There is a reason people don’t power houses with natural gas.