As soon as I read about the programmable I/O setup, it reminded me of the Propeller series chips from Parallax. The "cogs" that are the main processors of those chips aren't as general use as something like the STM32 cores, but they do certain things very, very well.
The P2 is a huge step up from the old propeller. If you haven't checked it out, I recommend it. "smart pins" are able to do all kinds of things, almost like having mini cores along with the main cogs. I used it for a project and was able to achieve all my goals. Really happy with it.
You've got me intrigued,but also wanting more specifics. Did you share any details of this anywhere you can link to? (don't worry if not, I'm just nosy)
https://www.parallax.com/propeller-2/ tons of improvements in terms of memory access etc, but pay attention to the "64 smart pins" section specifically. I use them to buffer out sub-microsecond waveforms 3ms at a time. I send it off to the smart pins then my cog is freed up for other things. I also previously used some for an HDMI GUI.
