Hi, I am the person running this project, I’ve been around since a while bothering you in the forum/github 
As a quick update just to say that this project is progressing fast and I’m very confident about it going into production at some point. Currently we are backing-up 370 accounts daily, and we plan to increase it to 1k shortly.
And also if we do a mesh in one repository only one user would be affected Other reason of this is that we can have more flexibility with bucket placement policies, like moving important users to critical areas, adding extra S3-side replication to certain users, etc… The main problem of this is that we don’t get the full power of the de-duplication but as you said, is a fair trade-off.
Yes, for sure! now the orchestration tools are very coupled to our environment but my idea if this goes into production is to make it more generic and share it.
I will maintain you updated about any news regarding this project and feel free to contact me if you have any question