Inquisitor scale makes for fantastic Daemon Princes. I'm sure you can find ol Krieger 'Krash' Thrax on ebay or something. His big metal arms might be just what you're looking for....
Oh, and Terminator AND Dreadnought sized bases are both legal. The Nurgle Daemon Prince is mounted on a 60mm, but regular Daemon Princes still come with 40mm. Take your pick...