iPhone batteries are already pretty easy to replace. I’ve done it dozens of times for several different models. It requires two screws, a bit of heat and a suction cup, then a couple more screws and some pull tabs. Usually takes under 30 minutes to do.

I don’t know how you could make it much easier while keeping the waterproofing. Rossman is a highly opinionated guy and I appreciate his advocacy, but he also makes no attempt to be fair to the product designers and is very biased.