Thanks for all the replies !
Yeah, I'm not a great fan of tank liners, but I really don't think that bare steel is a viable option anymore.
Ethanol absorbs water on contact, so as soon as it's exposed to humidity in the air, there's a corrosion risk.
Now electroplating the inside of the tank is something I hadn't really considered.
Basically you just need to turn the inside of your tank into a little electroplating vat.
I'm sure there are complications to be overcome , but the basic idea is sound.