Re: ero emissions?
"The hydrogen will be stored in a tank."
And that's the part which is most problematic.
The car and powertrain part are relatively easy. Storing and transporting hydrogen at extreme cyclic pressures - reliably and safely - in such a way that the equipment will last at least a decade is a not-fully-solved materials science problem.
The liabilities (and PR damage) when a hydrogen tank inevitably ruptures are such that I'm pretty sure insurers will be hesitant to provide manufacturer cover.