Apparently Imperial Agents will be very different from the usual codex. While it provides the rules and detachments/formations (I think) for all the specialist forces of the Imperium such as the Inquisition, Officio Assassinorum, Deathwatch, Grey Knights, Adepta Sororitas, Cult Mechanicus, Adeptus Astra Telepathica, Aeronautica Imperialis, and even the Legion of the Damned, it doesn't replace the codex for say, Deathwatch or Grey Knights (or even Cult Mechanicus). Apparently, what they plan is for you to add not an army or detachment, but for you to add maybe say a small elite strike force of Grey Knights or Deathwatch to your Imperial army. Imperial Guard? Oh, your general just requisitioned a small strike force of Grey Knights to help fend of a Daemon incursion. Necrons waking up under a hive planet? Right, the Deathwatch's elite strike squad has just joined your Imperial Guard army and tanks for a surgical strike!
One of the ways you can also create an army is by building a fluffy and thematic core around your various Inquisitions and their respective power armored warriors appropriate to their specialization. In other words, you can have an Ordo Malleus Inquisitor lead Grey Knights into battle, Ordo Xenos lead Deathwatch into an alien hive and Ordo Hereticus lead your Sisters of Battle (Adepta Sororitas) into a city tainted with heresy. Stuff like that. Very fluffy, it sounds fun!
I'll update you guys when I have more details!
|You weren't expecting me, right? Eh...you were? Ugh, I guess everyone's watched the prologue for The Lord Inquisitor by now...|