IF this phone ever happens.... not bad.

That's enough

Getting a waterproofing rating might not be worth the cost with removable battery bays.

Ups the price, but it's not going to be too effective if the user is removing that plate often.

will it have a real boot? (like the pinephone: put a microSDcard, uboot and here you go)

Wondering the same thing. I would LOVE a replaceable battery, but I know I'm in the minority there. Can you even waterproof a phone with that feature? And if the answer is "yes, but it makes the phone $200 more expensive" then we've got an issue.

Let an aftermarket phone case solve waterproofing.

An interesting idea, but that would likely make this whole thing much larger. Kinda defeats the phone's best feature, right?

Better than opting everyone into a waterproofing feature. The removable battery is more important than that.

Enclosing a phone in an envelope will always be a more effective means of water sealing than all the design sacrifices you have to make sealing your ports from the inside.

We've been sold waterproofing for a decade at the expense of repairability, but good luck getting a warranty claim through when that poor internal sealing fails a real dunk test.