KidSnide
Adventurer
In contrast, when the PCs are trying to persuade a fully developed NPC, that character's motivations, loyalties are quirks are things that the players actually have information about. Reducing interaction with that character to a die roll seems like it loses a great opportunity. Instead, I want the players to think about what sorts of arguments that NPC would find persuasive, and I want to provide major adjustments (or auto-successes) to reflect that player consideration of the game world...
Sure, but note that this isn't exclusive with roll first, narrate second. There is nothing prohibited in roll first with setting the scene, being clever, etc. The players are free to eke out as much advantage as they can, using whatever information they have, up to the limits of what the table will tolerate. As you say, in the middle of the swamp, that might be very little. With the long-running NPC, it might be a lot. Then they roll. Then they narrate the result.
So what are you envisioning? The players tell the GM what argument they are trying to make, then they roll the dice, and then they role-play out making the argument? That seems strange to me. It's also a little weird having PCs tell me which places they want to look, then roll the dice, and then describe how they looked around.
Or is that not what you had in mind?
-KS