A thicker battery would need a new back built with a hump or standoffs across the whole back to increase the overall thickness to match the new larger battery thickness...
A modern cell phone is very different from the old flip phones and SLRs/large dedicated camera. Resealing modern phones after upgrades/repairs is one of the harder parts of the whole process with fiddly little sealing glue gaskets to maintain IP ratings.
Yes, this is solved. Samsung makes rugged IP68 phones with user swappable batteries that are thinner than an iPhone 17 Pro when factoring the camera bump [1].
My experience with phones like that are that they tend to fall apart when subjected to impact, which is pretty counterproductive to features like, I don’t know, being able to use the phone immediately after an impact (car crash, fall).
I've had a HTC HD2 that had exactly that[1] - an extended battery with a bump. It looked silly, but did its job and in daily usage wasn't that big of a deal, actually provided a resting spot for my index finger.
This is a solved problem and not an issue.