Trading? you mean training? I know the primaris was announced as having 3 extra organs, with something from the primarch project in them.
Sangprimus Portum - Lexicanum
The Sangprimus Portum
is an Imperium
artefact, that contains the genetic material of all twenty of the Emperor
. In the aftermath of the Horus Heresy
, the Primarch Guilliman
gave the Sangprimus Portum to Archmagos Dominus Cawl
, after charging the Archmagos with creating the next generation of Space Marines
. Cawl succeeded and the unleashed Primaris Space Marines
are taller and stronger than their Space Marine brethren, due to the fact that the genetic material within the Sangprimus Portum was even more potent than the Gene-Seed
descended from the Primarchs.
This seems to be how Cawl did his work. Though it leaves me wondering where the Emperor hid this second example of the primarch source template. Corax after all went through a LOT of hoops to access the abandoned primarch genelabs for the copy he ended up with, which was corrupted and lost.