The "practical constraints" are mostly just lies from competing industries. Case in point, a hydrogen tank is both volumetrically and gravimetrically denser than batteries. Loosely speaking, it is about 2000 Wh/kg and 1333 Wh/L. That's better than any li-ion battery.
It is plenty good enough to replace both BEVs and ICE cars. As long as it is zero emissions, it works.
Finally, FCEVs exist right now. Hypothetical magical batteries of the future don't. So this is a meaningless comparison.