I think the ace up the sleeve is PIO; I've seen so many weird and wonderful use cases for the Pico/RP-chips enabled by this feature, that don't seem replicable on other $1-class microcontrollers.

I'd rather have the Linux SOC and a $0.50-$1 FPGA (Renesas ForgeFPGA, Gowin, Efinix, whatever) nearby.

Wow thanks, this is definetely something I have to investigate. Maybe the Sipeed Maix SDK provides something similar for the LicheeRV Nano.

I'm currently prototyping a tiny portable audio player[1] which battery life could benefit a lot from this.

1: https://github.com/sandreas/rust-slint-riscv64-musl-demo