This use of odd fuels is not limited to hydrogen. Consider those pushing to power autos with ammonia (nitrogen trihydride). Decent source of hydrogen, easier to move as a liquid, decent energy density. However, it is poisonous as heck. Used to be used as a refrigerant. Every time someone's ammonia regrigerator would spring a leak, people in the house would die. Burning the stuff also tends to make some nitrogen oxides some of which produce interesting products like nitric acid. Part of the issue is that folks are over concerned with fuel aspects, forgetting downsides.
If it were up to me I'd be tempted to say let us figure how to make thorium fission engines,buy a car, run for 50 years off the fuel, then salvage the metals. No carbon, no methane, a bit of low level waste at end life but might be feasible.
Or more seriously put some sulfur DIoxide in stratosphere, 1-2% of what is naturally there, and cool the planet. The economics is workable....pump the gas in a pipe the size of a garden hose, cost $100 million a year (not billion, not trillion...) and emulate volcanos. Mind sulfur DIoxide, not sulfur TRIoxide which makes sulfuric acid.
Sulfur DIoxide makes sulfurous acid, much much weaker, volcanoes emit it, part of natural environment. And then go back to using gasoline and maybe getting batteries that don't need rare metals and charge fast and don't freeze.