One thing about the memory bus is that it is a perfectly good bus for devices. You absolutely can put something like a computer into a memory socket and use it

One thing about the memory bus is that it is a perfectly good bus for devices. You absolutely can put something like a computer into a memory socket and use it as a device. You simply latch onto a particular memory address that's not going to be used for memory and whenever you see that you know the memory bus is for your device. I don't know if this is merely form factor compatible or an actual device for a SO-DIMM memory socket but there really isn't anything stopping you making a DIMM socket peripheral device except the need for external power.