> Just wish the PIO had a bit more logic/registers.

Seriously. I'd kill for PIOv2 to be some RV32E subset. Hell, I'd take stripped of normal LD/ST instructions if that made it easier for them.

Ah, you want a Propeller [1]. Basically 64 really smart digital + A/D I/O pins driven by eight 32-bit I/O processors. Enough oomph to build an entire system out of. Quirky, loads of fun if you're into cycle-counting. Not cheap, though--$18 [edit: $13 Digikey] qty 1. :(

[1] https://www.parallax.com/propeller-2

That's one good example. The TI Sitara and OMAP PRUs in the Beagle(Board|Bone|etc.) boards are another example.