The first thing I think of is profiling and extended event type activity. If everything is encrypted in flight, at rest etc then what is the mechanism for legitimate 3rd party profiling tools to work?
The general public are becoming increasingly savvy with regard to data privacy. GDPR is explicit in specifying that security must take into account the state of the art. Some allowance is made for the cost though the art of the possible increases each year.
I personally think any weakening of encryption, regardless of good intent, is a road to hell. I know some white hat hackers and the way their minds work will always put them ahead of the security game. Black hat hackers will find any weakening of encryption to be akin to being handed a limitless, untraceable credit card.
I find it ironic that the greatest threat to privacy has not come from the expected criminals. It has come from Facebook and legitimate organisations using data unwisely and unethically.