You wouldn’t get to pick ‘which nations’. What I’m describing would be a blanket statement: If you implement a carbon tax you can sign into this Free Trade Agreement club. Any nation in that club automatically has the same FTA with every other country.
“A Free Trade Agreement isn’t something universally good.” - Totally agree, but I think we can also agree that it would create an incentive for countries within the agreement to trade more with each other than with outsiders. It would also provide an incentive for the outside countries to join the club (specifically after it has reached some critical mass).
Industries within countries could definitely be negatively effected because of the FTA. I get that. All industry will be negatively effected if climate change isn’t curbed though. This seems like a way to make a tangible policy today that builds economic incentives for a carbon free future. It does not require full world ‘sign off’ before you start. It can start with just two countries drafting this open-invite FTA and allow any other country into the club once they’ve proven they have a carbon tax.