The mod series is really cool, but there's always room for improvement.
How about this?
1. Turning a human into an Astartes is now just an operation... But with the addition of the Anomaly, you can create a special altar/table for the operation and a corresponding Ascension ritual.
2. Only the Astartes can use the Astartes weapons & armor- it can be linked to a gene.
3. The Astartes need an ideology/religion. In their case, it's the codices. Since there are many orders, the codices should differ slightly.