I don’t know if you follow Greyhawk Grognard and his blog, but I’m a fan of what Joseph Bloch did with his Adventures Dark and Deep materials - the “what if” version of AD&D had Gary Gygax stayed at the helm and created his version of 2nd edition.
In any case, the class which got my imagination going the most was Joseph’s version of the mountebank. His work inspired me to attempt an ACKS version for my campaign world, and I wanted to post it here and see what you guys think. I don’t know how well a mountebank would do in the depths of a dungeon, but I believe he’d certainly be a worthy class or henchman in any sort of city campaign.
For the build, the class is a thief 3, 1b fighting build (just like a thief). Of his ten thief skills, several were traded for more mountebank-suitable abilities and his hallmark “snake oil” ability I counted as equivalent to 2 slots.