A feature built in to sonarr whereby previous seasons can been moved automatically to another drive or network share after a designated amount of time would be awesome, basically an auto archive system.
I don’t see it happening. Asked many times (search for “archive” here and on github) in many variations.
If you’re ok with sonarr no longer seeing/tracking the episodes you could do this via a script I suppose. If it’s not drive sonarr can see, you can get creative with symlinks.
Can only keep asking as they say Don’t ask, don’t get.