So, Age of Sigmar is pretty much a bust for large scale gaming. However, I think the Warscrolls and adjusted rules would make for a fantastic Mordheim experience.
General Concept -
Mordheim, in the Age of Sigmar, is a Mortal Realm that survived due to the abundance of Warpstone Shards. The forces of Order, Chaos, Destruction, and Death now send their heroes there to claim as much of the incredibly rare material as they can.
So, a bit of a shift from the general Mordheim idea - instead of treasure hunters, you get small warbands of proper warriors trying to find useful artifacts and warpstone in the ruins of Mordheim.
Right now, I'm thinking about a simple system of limitations on warscrolls -
3 Warscrolls with no more than 10 wounds per scroll
1 Monster, War Machine, or Unique
All scrolls must be selected from a single Army under the Compendiums section. No Hero may have more than 5 wounds, and no hero may be a "Named" Hero.
Rules Changes -
Base to Base Measurement.
Cover - On, In, or Behind (so, if you are shooting past a wall, you get a cover bonus).
No sudden death - all troops deployed per Scenario.
Victory conditions based on scenario.
You'd have to modify the system of advancement, and you'd have to modify the injury and death system. However, I think it might be a fun, small scale way to play Mordheim again.