Did a search and found nothing on the subject.
A feature for the Indexer that I would like to see is really a simple one.
Most indexers give a limit to Free users and Regular users have a limit based on their contribution to the site.
Sonarr does a search request of all the sites all the time. Some indexers send back empty NZBs if you exceeded their limit. This has caused Sonarr to spend a lot of time and bandwidth pulling from an indexer that has cut you off. If there was a seting in Sonarr that would prioritize and then pull only from the indexer up to that number. I can see that a lot of server banging would stop.
Also, a setting that would be able to weed out a duplicates on each indexer might help. although that might not be a great idea since all indexers build the NZBs and one NZB from one indexer will fail while the same NZB name from another completes. And yes, from the same provider. That has happened a lot. I don’t use torrents anymore because I have been placed on a no internet ban for 6 months. I had used a VPN on my computer and a VPN in utorrents and I still got shut down. Tried to argue the case that I have CABLE and could watch the damn thing but they didn’t care.