USB-C charging boards should be a good upgrade. However, the usual Type-C sockets have shell THT pins going through the board, with a thin enough charger board, the shell pins will prevent the board from being flush. This asks for either mid-mount Type-C sockets (can still interfere mechanically + less space for charger components) or for some kind of cutouts to be added to the back board. Possible alternative - adding silkscreen polygons for spots which the user can drill out for a generic Type-C TP4056 board to be mountable flush. Same problem occurs with the bottom Type-C port, and would likely benefit from one of the solutions listed.