So, in Adventure #346, young writer Jim Shooter introduced some new Legionnaires, Karate Kid, who learned all his skills through practice and hard work, Ferro Lad, who was supposed to be the first Black Legionnaire, but the editors weren't ready for that, Princess Projectra and Nemsis Kid. Except for Karate Kid, I don't recall seeing analogs for these characters in the Imperial Guard. I based Onslaught's costume on Karate Kid's original brown gi. I spent awhile looking for an alien race in the Marvel Universe with metallic bodies, I came upon the Autocrons, and thought they could fill the bill. He can't change to metal, but he's all metal and has superstrength. I figure he's a young Autocron exchange student, who jumped at the call. The Princess was easy to visualize. We know that super-powers can appear in the Shi'ar, Electron and Deathbird prove this, so I made her Shi-ar and I figure she's a distant cousin of Lilandra and her brother. Her powers might keep her from ascending the throne, but she can still serve the Empire.
And there there's the nemesis...I call hiim Contra, and nobody knows (except us, obviously) that he's a Skrull. A Super-Skrull, to be precise, whose powers of adaptability have been amped up in such a way that he adapts powers to counter any force used against him.