Exchanging the lives of billions of people for the most loyal and strongest fleet!
Also, considering Wuying Qi's craziness, if his plan in the Empyreal Terminus Sector worked out, it was quite possible that he would do the same in other space zones!
When the worlds were purged one after another, the Imperium would become the second Covenant Alliance in the end; a larger Covenant Alliance that occupied more resources, except that all the puppets in the "larger Covenant Alliance" worshipped not the Pangu Clan but him and him alone!
Was Blackstar the Great planning to take care of the four families and even the Covenant Alliance in such a way?