I don't think sharing the image is necessary during development. I just add the Dockerfile to the repository and each dev builds their own image. If they are methodical they can pull the repo and rebuild the image at the beginning of their work day. Most times it will be rebuilt in a second because there have been no changes. If they don't rebuild the image, it will be the main suspect as soon as something breaks anyway, so I can't see this causing much trouble.

This is exactly what I do, just using Trusted Builds.

Right now one of my biggest curiosities, is doing mass deploys and unified logs. I've not tried to so it hasn't mattered yet, but it could be fun.

Personally, I git pull and I just have all the important repos [e.g. things with Dockerfiles that people want to be notified if they should rebuild] dump to chatroom notifications so people know they might want to rebuild.