> GPU compute units are not that simple

Perhaps I should have phrased it differently. CPU and GPU cores are designed for different types of loads. The rest of your comment seems similar to what I was imagining.

Still, I don't think that enhancing the GPU cores with CPU capabilities (OOE, rings, MMU, etc from your examples) is the best idea. You may end up with the advantages of neither and the disadvantages of both. I was suggesting that you could instead have a few dedicated CPU cores distributed among the numerous GPU cores. Finding the right balance of GPU to CPU cores may be the key to achieving the best performance on such a system.