I guess my head scratching issues is why go with a caveman theme? You go from a stick to a club+1 or a pebble to a stone? Do you get a dinosaur as a pet? If ya wanted to go the zombie route you could do a Left 4 Dead type game, or Cyberpunk or Steampunk or Fallout style. Hell or even do a Time Travel theme that uses all of them...
EDIT: looks to be a Fantasy/Dungeon game, but didn't you already do that with Dungeon Siege?
With Diablo 3 and Torchlight 2 pretty much sucking up all the limelight I would have stayed away from a fantasy/dungeon setting.
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