Replaceable battery and water proof is possible. Se this video of Louis Rossmann about this https://youtu.be/7k4AV7N5g3U

Yes, I think the same. Screws is way better than glue and tampe.

Steam deck battery is held with adhesive unfortunately. And replacing it is difficult according to ifixit https://www.ifixit.com/Guide/Steam+Deck+Battery+Replacement/149070

I hope with this legislation it will be easier to replace.