Should be noted that fuel cells are batteries. We can already eliminate this problem right away. But we must "wait" for future batteries for no reason at all.

No, fuel cells consume fuel; effectively they are oxidising it in order to make electricity directly. For a hydrogen fuel cell, you still need to add hydrogen when it runs out. Whereas a battery (in the accepted usage of the word) is self-contained - electricity can be pumped in to recharge it, but no fuel.

Fuel cells do not consume fuel. It converts hydrogen and oxygen into water. You can reconvert water back into hydrogen and oxygen. You can conceive of a fully closed-cycle system for this.

But it's not worth it, since you are just carrying a big tank of water for no reason. It is a smarter solution that a battery which does carry everything at all times.