Use the main processor and interrupt it for I/O
Use I/O channels aka IBM Channels
One of his themes was using a computer for IO as opposed to the channel architecture of the 360. My own philosophy is using the main processor for IO and when you run out of capacity, add another processor. This gives you a fungible pool of resources.
Thus, there are three ways of dealing with the outside peripheral world. Do it with the processor and take interrupts; do it with another computer; or use IO channels and programs a la IBM and run special programs that are always interrupting the central processor. I think his view of using IO Computers for the type of machines he built was the right way.