Why would you buy a used ev with half dead battery's, it doesn't make sense, i will stick with hydrogen as the way ahead
Why would an Ev have half dead batteries? Well maybe an early Leaf.
Most degradation is early on and between 5-12% up to 150k miles.
"Tesla's own data show Model S and X batteries retain about 90 percent of their original capacity on average over 200,000 miles of use."
Motortrend Feb 2023
It's worth noting that the above statistics are calculated from older less reliable battery tech, and that ICE vehicles lose efficiency AND performance as they age.
You might be waiting a while for a hydrogen car and even longer for somewhere to fill it up, just checked and there are 15 filling stations in the UK, (Shell are currently closing theirs so may be less than this now).
Just take the electricity that would have been used to make, compress, store and transport hydrogen and send it down already installed wires and use it more efficiently?
H² fuel cells might be an option as a BEV range extender, if you really need the range, but will add significant cost.
It does make sense for haulage due to the energy density, especially liquified, as compressed H² is less efficient, as long as you're planning on mostly using all your liquid in one go (and not letting any just sit in the tank, as it quickly boils away). For personal transport though I don't see a need to make anything more complicated than battery > motor, unless your making, selling and maintaining car parts.