Perhaps it would be like a Water group only Ditto when it comes to breeding. The males are more common, but if you put it with a Water Group Pokemon, it would be the Female of the pair. I guess the difference here would be the babies would always be clownfish.
They could literally make this work by adding a gender change ability. They could make it to where it can be activated in battle too, in order to avoid attraction and captivate and whatnot (or to allow them to use it when the opponent was originally the same gender). I could see it as an actual possibility. Its BST would probably be like 300 though or something lame.
"I am the voice of one among the silent who's tired of burning among the flames"