On the face of it it doesn't sound like a bad idea. Save some money and double-down on the utility of hand warmers. I loves me some cheap utility.

But I don't know as how I would use hand warmers for oxygen removal in long term storage situations. The ones that might sequester oxygen either burn something, charcoal or lighter fluid, or react oxygen with iron using salt water to speed it up.

I'm not sure that water in a sealed container is the way you want to go. It also has to be pointed out that one of the main products of combustion is water. Doesn't sound like a good idea.