I think whenever a Megacorp enforces ideology (or creates a similar empire by status quo in vassalage war or via releasing vassal) it should create a new empire, that is an oligarchy and not a megacorp. It's actively harming to create an empire, that will compete for the places for branch offices with you and isn't able to accept your branch offices on theirs'.
I think it should just force an alien empire to become an oligarchy instead, so there is a way to make aggressive AI adopt your ideology, but not create a competitor in the process, but a friendly trade partner.
I think it should just force an alien empire to become an oligarchy instead, so there is a way to make aggressive AI adopt your ideology, but not create a competitor in the process, but a friendly trade partner.