Does the MoPi (https://shop.pimoroni.com/products/mopi-mobile-pi-power) have any ability to act like a USP by recharging the onboard Lipo battery once it’s connected to mains?
Unfortunately not. It’s a feature they wanted to support, but it’s actually remarkably difficult to support any sort of charging unless they settled upon one particular type of battery.
Since MoPi is compatible with so many types of external battery. there’s no single charging circuit that would work across the board.