I can’t agree enough. I’d rather see this onboard than as an expansion board. Like you can select the voltage to request from the usb c cable and whether or not to fall back to lower voltages either in software or via jumpers, and then get it on the pin currently used for 5v.
This would open up a huge number of applications for which the XIAO is plenty powerful enough. Stepper motors no hot ends would be very easy to work with whether for ioT (think tasmota powered mini blinds os the ESP32 model) or 3d printing with only a single usbc cable running to the hot end he controlling everything there.