Yeah, that's certainly a possibility, yet I've never really liked doing that kind of thing (always seems less than elegant)...
Discussion
Thinking more about this--and I believe I may have a solution...
I could put "threads" on the end of the case where the USB port is, and then have a screw on cover for that area (that you could seal with an o-ring).
That'd maintain access to the charging port, while offering a weatherproof design for when the device is in use...
Will take some re-engineering of my current case design, but betting I could make that work...hmmmm...