It'd make more sense for him to be assault or sniper class. He's admitting that he's done bad things, but also saying that he wants to make up for it and help defeat a common foe to atone for his past crimes.
Whatever he did before, he's clean as snow for xeno-busting duty.
HE contacted XCOM offering an alien artefact free of charge, and then offered his services.Especially one who took the initiative to successfully hunt down a black-ops group like XCOM.A skilled and effective soldier willing to work with them is nothing to sneeze at, especially when you're facing the end of the world due to an alien invasion.Not with the fate of the planet at stake. XCOM really isn't in any position to be turning down qualified soldiers because they may have done horrible things in their past.
