Seriously, I just can't envision MP being a good fit on a 65xx system—too bloated and slow. It seems to me to be a solution in search of a problem. Disclaimer: I think Python is a garbage language, with a degree of bloat that would make Microsoft proud if they had been the ones to invent the language. That's my two cents and I'm sticking to it.
I was won over by Python after doing a few projects with it. The philosophy, or at least use in actual practice, is counter-intuitive to a lot of people coming from other languages. The real strength of Python is that it's so much easier to use than something like C once you get used to it, which saves the programmer a whole lot of time. The price you pay is that it executes much slower for some things, but for a long time now the limiting factor for most PC programming is human time not compute cycles which are plentiful and essentially free these days.
Imagine a programmer has the choice between implementing a program in C, which will take 100 hours, or in Python which may only take 50 hours. If the C version takes 1 second to run and the Python version takes 10 seconds, you could run the Python version 20,000 times before you regretted not writing it in C since you've still saved yourself time. A lot of things never get run enough to make up for the added time investment. In the cases where 10 seconds is just too long, you can always use another language. No one is arguing that Python is good at everything, just that you save time in the long run on some but not all projects. Some of the criticism of Python comes from people using it for things that clearly should have been done in another language from the beginning then whining that it's "slow."
I would disagree that there is a lot of "bloat" if you mean that it's bigger than it has to be for what it does. There are definitely size and speed trade offs, but those are made thoughtfully and offer advantages that turn out to be useful for a lot of people. As far as libraries go, there are good ones and bad ones like on any platform where you let the community create whatever they like. The really good ones like pandas and numpy are actively maintained and high quality. You can use those to process large amounts of quantitative data really fast since they're written in C, so you still get the fast development time of Python without losing as much performance.
As far as MicroPython goes, I didn't hear about this until they started putting it on embedded boards with 100-200MHz ARM processors. I think it only makes sense when you have that many cycles to spare. Running it on a PIC16 seems to be more of a proof of concept to show they optimized well than a practical application. It seems strange then to try to get this running on a 65C816 since you definitely don't have cycles to spare and the tradeoff wouldn't make much sense. On the other hand, I think all of us are here just for fun rather than any practical reasons at this point, so I say go for it if you think porting MicroPython will be fun.
One of those fast ARM boards I saw shows up as a disk drive over USB which holds your Python source. You can edit it right there without copying the file to your PC first then you can run it immediately on the board. The neat thing is you can unplug the board and hand it off to someone else and they can pick up where you left off since the board has the source on it. Something like that will never replace C in embedded, but that type of functionality, along with saving programmers time at the expense of performance, will be valuable in some situations.
