CEPH is already designed for distributed heterogeneous storage, though, which is one of the hardest things to get right. The question is whether or not it could work well with large number of cluster members spread out so far geographically.

It already has the algorithm to make sure that changes require as few data moves/copies as possible.

With any other system I worry that if some volunteer's data goes offline we're left in a dangerously degraded state // new storage comes online and the system stupidly starts an automatic replication of data to repair the lost redundancy or rebalance and it chokes the links between the nodes and causes the storage to have massive performance issues for the end users.

CEPH is meant to be designed already to avoid that.