A "better" design is one where the consumer can service the battery without having to use special tools and a heat gun. It is explicitly _not_ one which looks "sleeker" in the marketing materials.
You can do it with a hair drier and the suction cap that usually comes with the battery. Or you can take it to a store at any mall and they do it on the spot for you.
It's one of the easier things to fix. I could swap a phone battery easier than I could replace my door handle or repair clothing.
This is the thing that annoys me about these discussions. Be against arbitrary barriers to consumer repairs that have no benefits to the consumer? Totally on board.
But that doesn't mean that repairs/replacements need to be limited to something a random user can do without tools or at least with tools they're likely to have laying around their house. I've replaced batteries and had batteries replaced in my MacBooks a few times and it hasn't been an unreasonably difficult or expensive process.
I've had laptops with batteries you could pop out but they were relatively heavy compared to today's norms.
So basically there's an entire industry needed to support people (and mechanics/shops) who work on cars--including vehicles that pre-date modern computer controls and which are considered user-repairable. But somehow repairing a smartphone or a laptop shouldn't require any knowledge or equipment beyond what the average user possesses.
I'm sure it's technically possible to build a phone where the battery is easily replaceable and is highly water resistant. Difficult? Sure, but possible. If this regulation really does lead phone manufacturers to go back to the days of hand-removable backs or slide-out batteries then I'm sure they'll be investigating in R&D to get their IPwhatever ratings back.
Example: many GPSr units have replaceable AA batteries and support IPX7. It's not exactly rocket science -- a good locking mechanism and a rubber seal.
The GPSr crowd tend to be less obsessed by their devices being a fraction of a millimeter thinner than last year's model, though.
(Much as I love a good locking mechanism and a rubber seal, I can see it making the phone a little thicker than it would be was the battery non-removable.)
You can buy a Casio watch for about 20 USD that claims to resist water to 100 meters. The battery replacement requires a small screwdriver, does that count as user-replaceable?
Having a number of portable V/UHF radios, GPS receivers and assorted other bits of outdoor electronic gear, I have had a tiny bit of acid-free vaseline on any gasket or O-ring I could find annually. Has worked a charm so far.
(With today's rubber being what it is, I guess I could safely at least double that interval - but it only takes a few minutes, and the vaseline is effectively free, so...
My father's underwater flashlights from the 1970s had replaceable batteries and were quite water resistant, I mean from sea water, not just rain. Of course a phone makes it more difficult both for its shape and size, but hey, technology progressed a bit in 50 years.
Underwater flashlights sooner than not suffer from outgassing and tend to have pressure relief valves and multiple o-rings to keep the water out. O-rings do need a bit of maintenance but it's not a huge burden.
Why the dishonest weasel phrasing?