The PIOs really are a superpower for this kind of thing. Interestingly the RP2040 documentation mentions that each PIO uses roughly the same silicon area as a dedicated peripheral for something like SPI or I2C, so now that the concept has been proven to work in practice it would be amazing if the successor chip ditched most of the single-purpose I/O peripherals and replaced them with a huge battery of PIO channels which can each be programmed to do SPI, I2C, or whatever else as needed.