Hi there!
I have posted this question on StackOverflow some time ago: https://stackoverflow.com/questions/51858864/docker-compose-how-to-use-the-same-user-group-ids-and-names-for-containers-that
I believe solving this issue will be beneficial for your initiative, too. I myself don't have much free time these days, so I cannot be relied upon for solving this, but I can provide some brain power occasionally if needed.