And a mechanism to adjust your own tone maybe.
So you'd add that on something like the URR system? I'm not actually sure trying to put your own spin on one of several premade lines is actually preferable to a more vague system. You'll become an actor choosing how to deliver his lines rather then a guy making a point.
I like the idea of copying URR and adding a lot of variation depending on the character, but you can't prepare every conceivable sentence. I think you've got to use something vague for the edge cases so players can say weird shit.
So, you'd end up with something like;
"Where is the chef?"
"Why would i tell you, *insult*?"
You expound on the virtues of silence in the eyes of the anathi people. The elf looks amused. Offhandedly, you conclude with a mention of their genocide at your hands. The speech is full of dry menace.
"He's in the shower. Hey man, there's a therapist in Oldtown. I'm just saying."
The tattooed elf backs away slowly.
I think that flows pretty well.