Board Thread:Warhammer 40k General Discussion/@comment-37.152.33.225-20131111163502/@comment-109.212.128.96-20131218110001

At first, probably, but he would try to change in the long run. Guilliman is the best "Administrator" of the Primarchs, and the one who truly wanted Humanity to live well in a better society (Ultramar, the many cities he designed...) so he would probably try to change the Imperium without falling in a civil war, one step at the time.

Think of the Codex Astartes...