Hmmm. Gonna post my brain storming here for general critique, if you guys don't mind.
So for essul I plan on him pretty much requesting his superiors to allow him to leave his current mission and go back to any anti-cerberus missions they might have. A request I plan for the hegemony to deny him, outright, and instead order him to stay on his current spectre task force and attempt to find any information on shepard he can from naleena or her resources, since he's in a closer position then most of their covert agents are inside a council involved endevours. ((let's not forget that one prequel jacob game where the batarians almost killed the council. They are not in good positions with them at all.))
Now from here I am uncertain of what to do after this point, because essul doesn't want to turn on naleena or manipulate someone he feels he owes a serious honorary debt to. On the other, this is information that could help the hegemony, not just his military superiors, but for all the citizens on planets potentially "high value" in another terrorist attack, which essul feels are the most important thing in this whole thing, the normal people.
A scenario I've been playing with is essul basically coming to naleena and begging her to give him any potential information on shepard using her contacts, even offering to let her have access to the classified hegemony data he's been working on decoding in secret, and allowing her to decide what information would and wouldn't be sent about shepard to his superiors. He's going to show how desperate he is, but also how unwilling he is to break from his personal code of honor in protecting innocent people is, even if it means having to swallow all pride and potentially becoming a traitor to the council and the hegemony.