Ticonderoga117 wrote...
Or just "Why didn't they indoctrinate their thralls to not make AI's?".
But nope, gotta make another AI to fight AI's I guess.
ME1 told us that the more control you have over a subject, the less use it has. If the Leviathans permanently controlled every single thrall, they probably would have been useless as subjects.
As for the actual topic: The Reapers do leave behind a Vanguard. It stands to reason that either it or the Catalyst itself would have noticed a Leviathan coming to the Citadel (a giant squid flying to the Citadel gets more attention than some Prothean scientist using a secret backdoor). If the Vanguard wouldn't be foolish enough to fly right into some artifacts, it could just shoot any Leviathan that plays around.
Especially as what you suggest would need the Leviathan to stay there, as their control isn't permanent.