Cluster mode for TimeMachine

At the Bro workshop a year ago, we had a brief discussion of cluster
mode support for TimeMachine. The simplest design was a proxy that just
forwarded every request to each TimeMachine in a cluster, and then
merged the responses. Has anyone worked on this sort of proxy?

No, not really. We had a student making an attempt but I never saw
any actual code coming out of that. It's still on the wish-list
though, I'd like to have it as well.