A rough draft. Comments welcome.
Diplomats are minor aristocrats who have chosen the path of diplomacy and intrigue to make their way in the world.
Prime Requisite: CHA.
Hit Dice: 1d4.
Maximum Level: 14.
Base XP: 1,700.
At first level, diplomats hit an unarmored foe (AC 0) with an attack throw of 10+. They advance in attack throws and saving throws by two points every three levels of experience (i.e., as fast as fighters), but use the saving throws of thieves. They may fight with all weapons, and may fight with a weapon in each hand, weapon and shield, or two-handed. They can wear any kind of armor, and use shields. They may use any magic item usable by fighters.
When hiring people (employees, mercenaries, henchmen, contracting a sage, and so on), diplomats treat the market class of the city as one better (Class I markets remain Class I).
Diplomats start with one of Diplomacy, Intimidate, or Seduction.
At third level, diplomats gain the ability to Move Silently and Hear Noise as a thief of the same level; and a second choice from Diplomacy, Intimidate, or Seduction.
At fifth level, the diplomat gains the third choice from Diplomacy, Intimidate, or Seduction. In addition, any henchmen and mercenaries hired by the diplomat gain a +1 bonus to their morale score if the character is there to witness and talk about their deeds.
At seventh level, the diplomat gains command of voice: The diplomat gains a +2 bonus to reaction rolls when speaking. If this bonus results in a total of 12 or more, the subjects act as if charmed while they remain in the diplomat's presence. Creatures with a WIS greater than the diplomat's CHA are immune to this power (the diplomat will know they are immune).
Diplomats at seventh level are immune to non-spell charm effects, including those of other diplomats; and gain a +4 on saves vs. charm spells.
Also at seventh level, diplomats learn to Hide in Shadows.
At ninth level, diplomats can build a castle in the same fashion as a fighter.
Also at ninth level, the diplomat gains the ability to perceive intentions: The diplomat always knows the exact reaction result (Hostile, Unfriendly, etc.) of creatures, even if the creatures attempt to lie or conceal their reactions. Creatures with a CHA greater than the diplomat's WIS are immune to this power (and the diplomat will know they are immune).
At 12th level, the diplomat gains Leadership.
At 14th level, the diplomat gains the ability to Read and Cast Magic Scrolls as a thief of the same level.
(EDITS: Swapped both 11th level thief skills for the charm resistance at level 7.)