How to limit messages from a certain sender on an iPhone?

I want to limit the messages from a certain sender to 5 per day for example. I don't want to blacklist the sender because I sometimes need to coordinate. For reasons outside the scope of this question, asking the sender for more consideration has failed.

I have iPhone 6, iOS 12.4.4, and a local carrier (not a multinational).

How can I limit the number of text messages and iMessages from a sender?

This can't be done on any current, base version of iOS.

As you've found, you can either block or allow a user to send you a Message but that's about it.

Even Screen Time, which was enhanced in iOS 13, doesn't allow this type of granularity for Messages. You can try to find a 3rd-party messaging app in the App Store but not aware of any that do what you're looking for.