Why didn't the Emperor put Angron in stasis?

From Arkhan Land flashback we saw that he could put Angron in some sort of suspended animation despite the nails; why not just put him on ice (as geneseed donor) and leave Lhorke in command of the legion? From what we have seen Angron has been a horrible liability to the XII, I doubt they would have performed worse in the great crusade without him forcing the nails on the legion and generally dragging them down to his level (from soldiers to drooling animals). Even if Angron himself was a prominent fighter, I doubt his individual combat abilities compensated general degradation of the legion as military asset.