I'd be interested in playing a handler? The go-to guys between higher ups and field agents who have no official authority but get the shit done or do have official authority, that's even more fun
Would being a human regional governor working for the xenos be appropriate? I feel like having a big bad constantly in the story could lead to villain decay if all there is only just him. A game of escalation may be in the cards, if I could be so bold as to suggest it.