You are correct you can only choose an item once per the SM dex...but then again...you can have a Bolt Pistol and a Plasma pistol...so yer good that way...or you could have say a Frostblade and a power axe if you were a SW...giving you two Power weaps...
always a loop hole to exploit some where
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I am Wolfpack, my fangs are long, my hair grey with age...I am The Great Wolf...I fight with bolter and Axe, my armies vast, my word final. A true son of Russ, my honor above all, I hunt the heretic, the xenos, and the witch and slay them where they stand! My sons hunt our enemies,
slay them where they falter and bring their pelts to Fenris