Not sure if you have the same thing in mind I do, but i was thinking the logic can go like this:

1. you search for a user

2. client tries to get their info from your existing relays

3. if you don’t have any relays in common, your client can then use one of the big relays currently used as “defaults” as a bootstrap to look up which relays that profile does use

4. your client then connects to one or two of those relays at random so that you can reliably see their posts