An idea in its infancy.

There is some really impressive hardware out there these days and in particular I have in mind the Parallax Propeller. Here is a demo of one emulating a SID, at the same time as outputting some neat graphics to a VGA screen.
[ Show youtube player ]
I've also heard of people emulating the ZX Spectrum (an early 1980s British home computer) on these chips. Some projects even feature several of these chips working together:
[ Show youtube player ]

I wonder if these chips are powerful enough to emulate all or part of AGA. Then, adding a 68020 we're part of the way to implementing an Amiga 1200 quite cheaply, mostly in software.

From recollection, on the Amiga the way to read from the keyboard and joystick and mouse, is by way of memory-mapped I/O. Many other computers of the era worked in this way. A simple ATmega328 or something could read in joystick ports (or maybe USB?), and write the relevant values into RAM when the processor is not looking at that particular memory.

Like I say, this idea is in its infancy. I do not have the necessary knowledge or skill to implement it of course, but maybe I am onto something here? :