Board Thread:Warhammer 40k General Discussion/@comment-5.65.81.205-20131002091720/@comment-3258762-20131115181634

Problem is: There were no Primarch Genomes. They matured as the Primarchs were created. He did not make Primarchs from Primarch genes, he made Primarchs from the best of all genes (and some Warp magic voodoo) he could find.

Secondly: Who would direct the Golden Throne? That was never what the Emperor had intended to do, it was for Magnus to be used. It would let Magnus roam the Warp as he wished whilst the Emperor could continue to rule the Imperium.

The Primarchs were vital to the Emperor's plan, and the Space Marines were just him trying to salvage the situation.