If they know what they’re doing, and know the questions they should be asking… then I don’t think anything. Well-informed adults can do well-informed adult things.
I admit that I was judgy about it when I was younger, and my elders were telling me they didn’t need a “purple crocodile” to short-circuit the dynamic… that when everyone opts-in, it turns what is normally a toxic arrangement into a self-healing system. It took years of convincing and lived examples before I came around to their point of view… today, I recognize that exceptionally emotionally articulate people can find a “you may remove your restraints and roam about the cabin” groove and happily occupy it for extended periods… until something happens. Which is when you discover the true nature of the relationship… on that one night out of 3,000 when that safeword would have been handy. How two people deal with that tells the tale.
Personally, I opt for the simplest thing that does the job: I tell them my name. And if I ever hear them use it, I know that they are 100% serious about the necessity of my undivided attention. On top of being a “pay attention” that automatically works, It means that even in a potential moment of conflict, she’s addressing me reverently.