Sandain said:
I would favor a multi-pronged attack.
This is my belief as well. The downside to this is, as a game, that your characters will be doing most of their adventuring separately. The upside is that it's probably the most effective means of doing what you're suggesting.
Before you begin, get a hold of a large wad of cash, perhaps the dragon's hoard that Sandain mentioned. That will help for the Faceman role.
Faceman: Your party faceman's job is to insinuate himself into the nobility. He needs to find out which nobles are for the king and which are against him. If any of the noble ladies are sleeping with the king, he needs to learn that as well. His job is basically to gain a working understanding of the various relationships in the nobility, to such a degree that he can manipulate them.
How does he do this? He steals a page from
The Count of Monte Cristo, and buys himself a foreign title, then starts throwing lavish parties in the king's capital city. He then uses his charm to begin working his magic on the nobles.
B.A. Baracus: B.A.'s job is to insinuate himself into the king's military, and ultimately his royal guard. His job is to understand the king's overall strength, and his internal security. He needs to know who can be bribed, and who can't, as well. Access to the king is not necessary for him to complete his job--which is primarily intelligence--but would be an added bonus, if achieved.
How does he do this? Ideally, there is a tourney he can win, to prove his prowess as a knight. Then he applies to join the king's guard, and based on his temporary fame and proven fighting ability, he's accepted.
Hannibal Smith: Hannibal's job is to infiltrate the castle staff. Aristocrats never pay attention to servants, so he has more freedom of movement in the castle to scope it out, as well as the ability to gossip with the rest of the castle staff. Also, there's always a believable reason why a king's guard or a foreign noble would speak to a servant, so Hannibal acts as the communication link between the various teammates.
How does he do this? He simply begs for work from the castle steward. It should not be too difficult for him to get himself a job inside the castle sweeping floors or peeling potatoes, etc.
Note: Hannibal's job can actually be better filled by a royal page. But that might be too difficult a position to get, since you'd need a very young teammate, most likely of noble blood. But if you can manage it, all the better.
"Howling Mad" Murdock: Murdock is your wild card. He stays on the outside and does his best not to draw attention to himself. Since the other teammates are going to be tied into fairly rigid roles, it's up to Murdock to perform any sudden tasks that need to be done outside of them. When nothing is needed, he spends his time chatting with the commons at the inn, or scoping the walls, or anything else he feels might be useful, but not flashy.
How does he do this? This job doesn't require any real setup. He can just get himself a room at a local inn and get to work. Murdock basically just needs to keep in touch with Hannibal to get his orders when they come, and other than that do whatever he can to learn more about the king from the outside. It's also a good idea for Murdock to have several possible escape routes planned out and prepared, in case things go south and one or several of the teammates need to flee the city.