In fact, this would be far better than the current approach, where these business units are largely unaccountable and hidden behind layers of corporate complexity (which eventually leads to dysfunction, which eventually leads to slower growth). Apple and Google could then spin off their own in-house app stores into independent units, which might even unlock more value for shareholders as these businesses would be likely to be valued at a much higher multiple than the parent.
This would be a way to get regulators and shareholders to work together to achieve the same end result. JPMorgan, Goldman et al would go nuts over the fees for the “AppStore spin out IPO.” Now that I think about it, that would probably be the biggest IPO since Alibaba, or whatever the last “biggest IPO” was.