The Inquisition: Inquisitor Tybalt looks more like a hive ganger than a member of the Holy Ordos, which is what led to the Slaanesh cultist before him in the interrogation room being caught. But the cultist can sense the stirrings of corruption in her captor, and will do whatever she can to fan those dark flames and escape, possibly with a new convert.
Alternatively, Tybalt and his interrogator are working on infiltrating a human trafficking ring that poses as a simple sex slave operation, but hides something far darker. Many of the people gathered by the operation end up as subjects in horrific experiments, but in order to get to these heretical secrets they will have to blend into the sex slave scene...whatever it takes.
The Imperial Guard: Commisar Venris spent his entire life in the Schola Progenium, training to be one of the elite, one day hoping to inspire a great regiment of the Guard to dizzing heights of glory in the name of the God-Emperor. His assigenment finally comes, though he begins to feel that he'd been punished. The regiment was a mixed-gender regiment, which was leading to some...complications. Worse, the commander was a female, tough but fresh to command. It's up to Venris to keep discipline and help her gain control of her regiment, before they're all killed.
Rogue Traders: You would play a female Rogue Trader, a tough veteran who has already amassed a fortune, as well as a veritable army of rivals. I'm your second in command, your Seneschal, a master of spies and secrets who helps you with your adventures (as well as keep you company in your chambers). I hear about an uncharted planet that may yield considerable wealth, but inform you that it will be a race to claim it before anyone else does.
I'm up for other ideas as well, if you have them. I'm also willing to tweak these however we need to. Feel free to message me if you need more details on any of these ideas.