You can't run a GPU without a CPU, but you can run a CPU without a GPU. Could we change GPU's so they become more general purpose? Yeah, an we already have by

You can't run a GPU without a CPU, but you can run a CPU without a GPU. Could we change GPU's so they become more general purpose? Yeah, an we already have by gluing the GPU to a CPU ie integrated graphics, lots of CPUs has that. But when you do that we call it a CPU and not a GPU, so as soon as you make a GPU general purpose we start calling it a CPU.