Thats actually a great idea. Imagine actually being able to talk Ghandi down from nuking everyone!
Another huge problem is the extremely questionable affordances in free form speech. Here's an NPC, go talk to them. But about what? Maybe they drop clues. But what if the player doesn't pick them up, or they're distracted and aren't paying attention, or it's been 2 weeks between play sessions and what was this guy's deal again?
[clap emoji]x3