Breakout characters happen more because of actors than the idea behind the charatcer. Then the writers catch on and start writing more stuff for that character. Thats why Weyoun came back from the dead (and the Vorta gained the whole clone idea as justification), why Garak was practically a regular and why Damar developed far beyond a tertiary character.
And none of those characters were the Spock type comment on humanity. Garak and Damar were more comments on Cardassians than humans, and Weyoun was simply a very alien sort of critter, who played by his own unhuman rules. Aliens like that are what Trek need more of - actual aliens, not humans is disguise.
Or, just have them be humans. The breakout charactter on ENT was boring old human Trip, due to Connor Trinneer's charm and talent. The other breakout was Phlox, again, due to the talent of the actor.