Turgenev (of Dragonsfoot, not the author of Fathers and Sons) has done some interesting tweaks on my recent version of the Mountebank. He takes the level chart up to 36, adds some great level names, and other little riffs. You can his download the PDF of it here.
Also Joe Bloch has his own nifty version of the class up as part of his vision to revive the Gygaxian second edition. Check it out on Greyhawk Grognard.