If I'm not mistaken, this problem is exactly what is attempting to be solved by the current anti-trust suit against the big tech companies in the United States (this is the suit brought by Texas and a few other states). Depending on the outcome, vertical integration like you're describing could be deemed monopolistic and result in Google being spun off into separate entities for each of the parts you're describing.

I think views related to this topic somewhat depend on whether or not you consider Google a monopoly in the digital advertising space. If you do, it would seem that bringing more of the world in-house would be deemed illegal under anti-trust laws.