One of the big advantages you
One of the big advantages you get with hydrogen gas over a liquid is safety.
Yes, contrary to popular images (Hindenburg) a gas is safer than a liquid because in a crash, the hydrogen gas quickly evaporates into the atmosphere unlike gasoline which pools to the ground and engulfs the people in flames.
I also hesitate to think why you would want to take an harmless gas like hydrogen which is perfectly useable and replace it with a toxic poison like hydrazine.
No. I don't like this idea at all...