Sounds like you are 100% aware of the possible issues. 
I’m curious how you handle this though. I have for long been looking for a “Followup solution”. Ie, if I don’t get an answer within X days, I need to followup on that client.
Actually, I asked the community about this a while ago: Boomerang for Apple Mail?
I want the “Always follow up on emails after no response” function.
Both Mailbutler and SaneBox are not good enough though.
Maybe you have a better solution?