1) Where can I see a formal spec for this field? There's a d8 module called select_or_other which I tried but it had a nasty bug so I'd rather wait for a fix.
2) I fixed this by creating a new module called geolocate_element. I'll need to put that module on the system, and document it a bit and I've got a lot on right now, so again, I want to leave it for a while.
3) This seems non-urgent, but is a reasonable request.
Lets wait for a drupal 7 commit and maybe work on them together.