I'm starting to suspect Delos doesn't give a fukk what Ford does, or what happens at the park, as long as the hosts keep becoming more advanced. In the first (or maybe 2nd) ep Theresa said Delos interests go far beyond the park. Like @Norrin Radd mentioned Charlotte said it again this ep.
So I don't think it's a matter of Ford stopping them, I think it's a matter of (so far at least) they're letting him run wild to further their own goals.
Fred.
They want things to get more advanced but they also want to replicate the tech outside the park and can't, that's why Theresa was stealing code. They let him do whatever he wants because if they stop him they lose all his work since he controls everything, literally, and can shut it all down in an instant. Since that would be a waste of everything they invested they leave him to his own devices while making plans to get rid of him while keeping his work. If they ever beat him that thing you're worried about with people being replaced will be possible, right now they can't create hosts outside the park and Ford controls all the hosts made inside the park.