[3.5] Good class for a mob boss

[Voice of Reason]

A marshal sounds like your best bet, what with descent physical stats and those ever-so-much-fun auras. I'd say to give him a charisma score primary and use the minor auras to cover his skill bonuses, with wisdom and intelligence your tertiary choices. It would keep him reasonably intelligent and keep him from becoming too much a melee threat in his own right. A marshal would work really well in the fluff too; as the mobster changes tactics, so too would his auras:

"You look like the kind of guy who could use some...'protection'" [minor aura: charisma]

"I'm sorry to hear that..." [major combat aura]

You can afford to add a level or two of rogue if you need him to be a bit sneakier and less direct.