As a Dwarf, Beast gets bonuses to Health (+10%), Evasion (+5%), and Sneak (+1), as well as the very mediocre and overpriced Petrifying Touch.
More health and evasion are good for Warriors and Rogues, and the Sneaking also helps a bit with Rogue. Petrifying Touch is saved by Magical Armor, which is not a good fit for physical damage.
Really, you can make him whatever class you want, but since your friend is going magic, going physical would probably be a good fit.
I am currently running Beast as my Avatar, and I specced him as a Rogue, taking Parry Master, and focusing more on Dodge than attack power (Dual Wielding), with some utility skills from the Aerothurge line (Favourable Wind, that 90% evasion skill, Teleport).