> Having it run on a pico would be pretty impressive

Yes, although relative to the DECTalk DTC01, a Pi Pico is a beast !

Pico : dual core ARM @ 133 MHz, 2MB flash, 264K RAM

DECTalk: 68000 @ 10 MHz + TMS 32010 @ 20 MHz (5 MIPS), 256K ROM, 64K RAM