From what I know of him he's an even more powerful clone of Superman, and when Superman or one of his Super people are around it kinda takes away from the rest of the Legion. Since I'm likely taking Starman/Starboy now, there's a few characters that fill the strongman of the group spot like Ultra Boy, Andromeda, Kent Shakespeare, etc. If there was more info on Superman X, like in the comics, and we had something more to base him on it'd be different... but from what I understand he's a little bit clone Superboy, a little Eradicator, and a little bit Mon El. 

Or you could just use him as inspiration and make an original clone or Daxamite. 

~KL~