What would be the character's motivation for joining XCOM? I don't know how much XCOM pays, but I doubt its well publicized and just doing actual piracy would probably be easier, and possibly safer and more profitable as well.
Especially with the amount of pure carnage going on in certain areas. Places on high alert leads to looting and rioting, people paniking leads to security risks and not looking where they are supposed to.
Honestly, it would be better for the Pirates to stay away from fighting aliens, as they could rise to power very quickly by staying organizing and making strikes on high value targets to steal them
I don't think the character concept it very sustainable or even valid at this juncture.
Now, if they were a higher ranked Pirate from Somalia or another ocean bordered African country, ti might be easier to show them as trying to turn over a new leaf and leave that life behind, or even being forced to do so as a prisoner exchange (Like Steve was), maybe serve with us or that death sentence/hands getting lopped off goes through.