The "Secret" of the PicoMEM/PicoCPC is its multiplexers. [https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/picocpc/msg249997/#msg249997 Source]
It allow to limint the number of I/O needed and act as a Voltage converter at the same time.
The Pi Pico allow to have multiple PIO core, plus the main core working together in parallel,so the PIO manage the Multiplexer, reconstruct the Address, while CPU core detect and manage the Control signals, Read in advance the High part of the address to jupt to the correct code.
(IO MEM Read or Write, Bank number)