I appreciate the effort here. One major flaw I see in your argument is ignoring historical context. You point to the CPC being very wealthy and owning a large amount oy stock and businesses and use that to argue other parties should too, but you leave off the how and why the CPC owns so much. It wasn’t as you argue others should do, by out competing capitalists, but rather due to their actions after their successful revolution. I’d suggest elaborating more on this to see if you can reconcile some issues in your proposal. Additionally I’d consider how capitalists are trying currently to do what you suggest the communist parties do, to essentially buy out all competition.
In a pinch this is a viable strategy, particularly at stores and restaurants. They often throw out still good food.