I've built a new list, based largely on Chroma's Cadian Defence Force (entirely without any consent from him!
). Cadian Interior Guard
The list is designed to allow a Guard army with Inquisitorial allies. This is a consequence of removing the Guard allies from the Inquisitorial forces. Why Cadians? With the proximity to the Eye of Terror, the Cadian army maintains very close ties with the Ordo Malleus, who maintain a standing Inquisitorial presence very much integrated with the local military.
As I said, based largely on the existing Cadian PDF list, I've added my own tweaks to it. Compared with the Steel Legion, it lacks tank, artillery and superheavy tank companies, but gains stormtroopers as core formations plus Inquisitorial support. Rather than the fortifications of Chroma's list (not a bad idea) I've simply added a Mobile Fortress, which rather gets that idea across.
The Cadian Inquisitors simply have retinues of Kasrkin as they are more militaristic and not likely to be bringing rag-tag desperados with them.