And don't forget it's way faster to refill a hydrogen tank than an battery. Also, cars are such a big industry it's actually easier to not have a middleman (hydrogen -> electric grid -> EVs) because all the infrastructure would have to be built without any real need for it.

I agree with everything you said except the retrofitting... I don't think retrofitting an ICE is going to be remotely possible for any price anyone would be willing to pay. Sure they both have a "gas tank" of sorts, but as you mentioned, a hydrogen vehicle is ultimately an electric vehicle... And electric motors and their supporting components are quite different than ICEs.

Except the cost to refill with Hydrogen is significantly higher than petroleum in many parts of the world, which makes it non-viable as a fuel. A Lithium/Sodium battery can be charged by whatever fuel source you want and can be done at home. Hydrogen can only be "charged" at a hydrogen fueling station, which has to exist. All but one Hydrogen fuel station in America is in California and there aren't even a lot of those.

Hydrogen fueled vehicles are a cool technology, but they aren't practical and thus will never sell anywhere outside of Japan. My point was that Toyota could make a car that works everywhere and just swap engines in a Plug-in Hybrid for the fuel source or, for fully electric vehicles, change the power generation source. If they make the power from Hydrogen and harvest the salt for sodium batteries, they can make two parts of the water they're harvesting from the ocean into useful stuff.

They've been making claims about their solid state battery for years. It's always a few years away.