In defense of my previous post, it is the only way I could see it working.
I wouldn't personally do it, but if I were going to, its how I would.
All that said, I think that an individual who has displayed the level of trade craft, versatility and skill could be a threat on the inside of firewall (Prometheans be damned), but it would require him having gotten in from the earliest days, having subverted Eye Rep at a fundamental level, and having built personal influence across the entire conspiracy. Certainly no easy task.
Is the idea of a threat attacking firewall in that matter completely beyond belief? Hell no, firewalls two greatest weaknesses are its belief that it has managed to make a structure that can't reasonable be compromised, and B, the belief in the 'infallibility' of the Prometheans, by those few that know of them. But Manjappa doing it? Nah, that is just strains credibility to much. You get to pull of one impossible superspy routine, and then your done