I think I misunderstood you earlier. So if I understand correctly, my client can still talk to your relay like a normal NIP 50 search relay, while the NIP 85 provider is what gives your relay the trust data needed to filter the results. Does my application need to implement any NIP 85 specific logic itself, or is it enough for my npub to subscribe to a provider like Brainstorm and then connect to your relay normally? If it is the second case, that is actually exactly what I need.

All your users can select their sources of trust independently. Your app doesn't need to do anything special besides authenticating with our nip 50 relay and making sure users have their outbox relay lists set correctly so we can find and index their events.