Tanks inside aren't subject to as much stress as the hull of a ship, since they are usually made to be pressurized or work in tension. With stainless you have to be a lot more careful of temperature gradients placing stress on joints/fastening.

I'm just not a fan of stainless as structural parts. I weld enough stainless used in various safety related systems to just hate it. Customers wonder why the parts come out so funky, when they are requiring at least 5x too much weld on pieces and don't understand that stainless warps way more than carbon steels. I think you could make it work, though, but it would require better engineers than I'm used to working with to pull it off.

Proper venting would reduce/eliminate any hydrogen concerns, especially if you double or triple seal the batteries, or use sealed batteries for a majority of your power storage.