PWM? Anyone ever get it working? Even via peek/poke directly at control registers?

Potentially someone could make the UtilTimer in jsharware.c do this using the hardware timer and interrupt - that's what it was originally meant for. It's like 3 functions to implement and then you can have proper soft PWM.

Since each strip -- and there are many -- needs its own MCU, it simply isn't financially practical to do this with the official boards

You know the price goes down a lot if you order directly, and in bulk? If you buy 100 it's £12 each for the Pico - so I guess it depends how many strips you're doing and how much you think your time is worth ;)