A single master indexer could write to multiple PC2.0 specific relays for redundancy. You could have several indexes doing the same thing if you wanted to be more immutable. Similar to how bitcoin's ledger is replicated across all the nodes.
End user facing apps simply need to connect to these relays to access the feeds?
I'm saying all of this will little technical knowledge of what's truly going on in the background so I could be entirely full of shit. But this seems to be a simple starting point?