This is one of many reasons why I think phones should have easily replaceable batteries. I'm on my second Note 4 since launch and couldn't be much happier.
The problem with easy replace is what a lot of old phones had - a drop and the battery comes flying out too. Obviously, this has gotten a lot better since then, but I think there is an advantage in design for daily use for not having batteries being easily accessible to the end user. What Apple should offer is easy battery replacement for a price that isn't marked up significantly like the rest of their products, and treat it like a free maintenance plus the cost of the replacement part.
While having it externally accessible for trivial swapping is nice, the obvious downside is that it can come out inadvertently. A compromise where it is behind a screwed down panel and held in place with a connect (not soldered). This would mean easy replacement either by either by the end user, an authorized repair shop or apple. I don't really see this as any different than routine maintenance and replacement of car parts. If Apple charged 5x battery replacement costs compared to other phone vendors then this might cost them marketshare, however, people still buy fancy cars where parts are much more expensive.
This is what Apple does. They'll replace your battery for $79. Third parties will do it for a bit less. Doing it yourself requires a weird screwdriver and some other tools, but isn't terribly hard, and you can get a kit with a new battery and all the required tools for $25.
My 7 year old Kodak Play Sport waterproof HD camera has a removable battery and has no problems being submerged at the bottom of a swimming pool. I'm confident that Apple could figure it out if they wanted to.
