Rokugan had the Courtier class, which exactly does that but is also a skill-monger (8 skill points per level, not so long class skill list but every 5 levels you get 2 more class skills to expand your list).
IMHO it's a very cool class (but be warned I'm a fan of the setting) but indeed such character can be both either underpowered or overpowered depending on how the DM setups the game.
That was indeed one of the games I was thinking of when I came up with it. 7th Sea is another one that also eventually created "social combat" rules to give interaction it's own mechanics as in-depth as combat gets.