First I see many Cubans being able to eat and buy medicines. Open investment will help the vast majority of Cubans. Why hasn't this happened before now? Castro can trade with the rest of the world. Many countries did.
Second, I see Castro's biggest excuse for his failure taken off the table.
He can substitute another one. Who's going to object?
Well, the vast majority of Exiled Cubans live in the US, not in other parts of the world. They are the ones who would send capital into the country. The trade between S Fl and Cuba alone would be larger than all other trade combined. Your argument would be analogous to saying "Let's shut down all the supermarkets within a 500 mile radius of a city, and if the citizens of that city really and truly wanted to eat, they could and would go beyond the 500 mile radius".
Castro's main argument against the US for 40 years has been the Embargo. He is 100% PRO-Embargo.
Maybe now you can defend the Embargo, the one Castro relies on and supports more than any other person on earth.