Jürgen Hubert said:
Why?
I'm not trying to be snarky - I am genuinely curious. Would you be bored by it? Or would it involve too much preparation for your tastes? And have you ever attempted something like this - or played in a game with such plots?
I have played in games with political intrigue and have enjoyed it. The thing is, the main reason the intrigue works is because there is something preventing the PCs from using other more direct methods to accomplish their goals.
What I have not done is play in a game where the PCs can pretty much do what they want because they are clearly more powerful than most anyone else and feel fully justified in doing it because they are changing things for the better. So, they have the power and the motivation, where is the challenge?
As DM I could create ethical challenges, but while I've found the occasional ethical dilemma can be a nice change to play, a constant diet of it quickly becomes uninteresting.
I can play up the challenges of building a government, but if the PCs are just going to have to deal with squabbles of low level NPCs and events like making trade agreements for food, what is the point of getting the PCs to 20th level in the first place?
The players need to be challenged. The challenge needs to be appropriate to their power level, or else it isn't a challenge (that's why 20th level PCs don't get XP for killing ordinary orcs). D&D provides a decent set of rules to help you determine an appropriate challenge for PCs, no matter their level. I don't have the time or interest in wracking my brain trying to figure out how to create a challenge for the 20th level party using a level 8 Aristocrat/Level 3 Fighter King and his people that the PCs cannot just walk over to, drop some spells and wield some weapons to effectively remove.
I am also not trying to be snarky and am curious. How do you keep the players challenged if you don't give them bigger monsters, and face bigger threats? I can easily envision the game becoming:
"We want to remove Evil King James and free the people of his land."
"OK, how?"
"We'll Wind Walk into the castle, I'll hit him with a full attack with my +5 longsword while the rest of the party laughs at the feeble attempts of the guards to hit us."
"OK, he's dead. The guards surrender, but the people are angry. What do you do now?"
"I take his crown and, since I cannot be bothered to run a kingdom, give it to his bastard child who, according to a Know Alignment spell, is Lawful Good."
"Great now what do you do?"
"We heard there was a drought in the kingdom to the south. Lets go by and drop off a few of those decanters of endless water we made last month and let the people revere us as saviors. After that, we'll go remove the Tribunal Rulers of Gothmarg, they are only 9th level and they allow slavery."