Such a product does exist, but I'm not sure that it handles "merchants and politics and such" any better than any other system so far recommended. In fact, I'm not sure that any of the systems so far recommended (including those that I mention) contain substantial mechanics for addressing these things past a simple skill check.
In other words, when you get right down to it, none of the systems so far recommended will handle the social aspects that the OP addresses much differently than D&D will (i.e., by asking the players of the interacting characters to make X skill checks and compare results).
There aren't too many game systems out there with highly developed rules for handling social interaction. AFAIK, only Burning Wheel and Exalted 2e have explicit resolution rules for social interaction that are notably different than the respective core task resolution system of each system. Well, and maybe the old Baron Munchausen game — but a lot of people don't consider it to be a RPG.
"The Company Rules
Much of the hype surrounding Reign prior to its release has been about the company rules. Those rules are designed to allow players to take control of countries, guilds, tribes, brotherhoods, or whatever else along those lines you can think of. Although it’s always been possible for gamers to roleplay those situations, Reign is the first game (to the extent of my knowledge) to provide mechanics to support and promote that sort of play. For simplicity’s sake, the author has chosen the generic term “company” to refer to any sort of organisation that might make use of those rules. Therefore, keep in mind that the term “company” here can mean a small band of mercenaries, a powerful merchant’s guild, a great nation, and everything else in-between.
Each company is made up of five attributes: Might (military prowess), Treasure (wealth), Influence (political power), Territory (the land, its value, the population, its culture and its technological level), and Sovereignty (the people’s loyalty to the company, the strength of their common identity.) Each attribute is rated from 0 to 6, with the exception of sovereignty which must be at a minimum of 1 in order for the company to actually be a company rather than just a group of people not united in any way. Along with a short description of what each rating means, each attribute gets presented along with a few examples of how you can temporarily raise that attribute. For instance, you can raise Might by using scare tactics, or increase Treasure by asking for a loan.
Rules are also provided for combining and dividing companies, and on how to improve each attribute. What’s important to understand here is that the attribute scores are exponential in nature. A Might of 4 is not a Might of 3 plus a Might of 1 – it’s more powerful than that. The end result is that there’s not much to be gained in forcing a much smaller company to combine with your own, just like a schism that divides your company in two will not necessarily reduce your attributes by half. Although those rules fall a bit on the technical side, they do a really good job of simulating those kinds of situations in a way that feels more than purely mathematical. Besides, those sorts of events are not likely to happen every game session.
But what do companies do, exactly? Well, anything you design them to do, but the rulebook provides ten examples of actions a company can take : Attack, Being Informed, Counter-Espionage, Defend, Espionage, Improve the Culture, Policing, Rise in Stature, Train and Levy Troops, and Unconventional Warfare. The result of a company’s action is resolved using the same ORE system as with the rest of Reign. You simply combine two attributes relevant to the action (like Might + Treasure in the case of the “Attack” action, for instance) and roll your dice pool away. Here’s the kicker, however. Each time you use an attribute during a month, it decreases by one for the rest of that month. For instance, if I have a Might of 3 and a Treasure of 2, my first attack will be with a pool of 5d10, my second with a pool of 3d10, and my third with a pool of 1d10. It makes sense. Resources get spent, troops get tired, and so on.
A very important part of the company rules is how the individual PCs can influence the outcome of whatever action the company undertakes. Through their actions, they can give the company bonuses (or inflict penalties upon it if they fail whatever plan they had to help the company.) Those bonuses and/or penalties act as a sort of interface between “regular play” and “company play”, as the adventures the PCs undertake can very much be about helping the company achieve its goals on a more personal, character-centered level. Inversely, the company can be used to help along whatever adventures the PCs choose to undertake. Need information? Send some spies. Want to infiltrate the palace of Baron X in order to steal his treasure? Use the army and besiege the mansion of Count Y to make sure he unlocks the door and lets you in the next time he visits his good friend Baron X. And so on. In the end, it’s all good. The company rules have a nice flexibility to them, allowing companies to either take center stage or be just another tool for the PCs to use. Or both. Either way, the last page of the company rules provides advice on how to use companies to support all those various modes of play, along with suggestions on how to pace switching between PC-centered play and Company-centered play.
Overall, what impressed me the most about the company rules was how underwhelmed I was by them. I know it sounds a bit contradictory, so I’ll try to explain. The company rules feel incredibly simple. They make perfect sense, and each part of the whole feels like a logical design decision. Reign is the first game to feature rules like that, and I sat down to read them expecting an extremely clever bit of game design that nobody had ever thought about before. There’s nothing especially clever about them. They’re a logical outgrowth of the ORE system produced by the design goal of modeling “companies.” The same thing could’ve been done with Unisystem, Silhouette, d20, Synergy, you name it. Kudos to Greg Stolze for taking a design goal and herding it towards its logical end result. Ultimately, I think that this sort of methodical approach makes the company rules accessible, which is their main merit. The rules allow you to rule a nation in a way that feels detailed without bogging you down with minutiae like the exact number of troops, or the value of your exportations. And, more importantly, that level of abstraction allows for the action of the individual PCs to have a concrete impact on how things go for the company.
The best thing about the company rules, however, is how modular they are. You can just take them “as is” and slap them on top of whatever game you’re playing. It’s as simple as that. Since they function on a whole different level than “regular play,” you don’t even have to change the rules to adapt them to the system you’re using."
from
RPGnet : Review of Reign