How deep is the grudge between Ministorum and Mechanicus really? Could you reasonable have them fight alongside each other without autistic backstabbing? Could individual members of both organsations become friends, for example if they are working together as acolytes of an Inquisitor? Could there even be love?
In a Dark Heresy game we both felt the other had joined the wrong priesthood and subtly tried converting the other but mostly we were bros engaging in JOLLY COOPERATION
>Could you reasonable have them fight alongside each other without autistic backstabbing?
Yes, it happens all the time with Guard auxiliaries.
>Could individual members of both organsations become friends, for example if they are working together as acolytes of an Inquisitor?
Yes.
>Could there even be love?
NO THAT'S HERESY
REEEEEEEE
The grudge between the Ministrorum and the Mechanicus isn't all that bad at all. The Mechanicus still provides Sisters with power armor and vehicles, for example, and does not sabotage it or anything. Likewise with pilgrim vessels (spacecraft) and big stonkin' power chainswords. They have doctrinal disagreements, and some Missionaries secretly try to convert Machine Cultists, but for the most part they get along just as well as any other subjects of the Emperor.