Maybe some clients would provide the following:

- There would be a service that keeps the most updated profile lists across as many relays as possible with the relays they have used for their latest posts

- Your client, would save your "Follows" and would check against that service if any of your follows switched to a combination of relays that have no overlap with you

- You can then check the people you follow and get a red flag or warning for those you may no longer see and what relays you should add

That service providing the list of profiles could be good so then you can search for people regardless of what relays you have and then decide if you need to add more relays or not