Why not just build what you want. I've been riding this for 4 years. It is an old Specialized RockHopper "citi-fied" with dynamo front, nexus7 rear, fenders, and rack. I've not seen anything better yet.
Because it can be cheaper to get it off the rack already built up (if buying new, anyway). I've seen bikes just like yours that came that way from the factory.
Not many, though, and not necessarily using a MTB frame, but they're there.