Poompop is just a fun comic relief character that provides a break after all the heavy material in the opening mining camp. He's also the reason for Crystal and Daniel arriving at Exile before the Remnant, even though the Remnant left Oasis first. I also threw him into Sol just for fun. People seem to like him!
I thought about putting him in the ending, maybe if you waited long enough at the ending screen. It was going to show Oasis and he would arrive and say something like "Finally, I made it to Oasis! Now, what did I want here, again? ...Oh well!" and then he would leave. So there's the official word of what happens to him.
I decided I'd rather not have a joke for an ending so I left him out. I like it leaving the player thinking about the new lives that the main characters have found.
I can see why you think Poompop might be an evil kefka/joker genius! That's the vibe I was going for with Zethros, where at first you think he's just crazy.
