Since the USB-C port often supports bidirectional power, it may not actually make it that much larger, if at all, as the battery charger IC can often operate in

Since the USB-C port often supports bidirectional power, it may not actually make it that much larger, if at all, as the battery charger IC can often operate in "reverse buck" mode to turn the battery voltage into 5V, which when using synchronous rectification (almost mandatory for efficiency now) means it has all the parts for forward boost, and just needs a slightly cleverer control IC. This is like how many modern power banks can use the same inductor for buck (5V->3.7V) charging and boost (3.7->5V) discharging. Check this app note from Intersil/Renesas: https://www.renesas.com/eu/en/doc/whitepapers/power/usb-c-buck-boost-battery-charging.pdf https://www.renesas.com/eu/en/doc/whitepapers/power/usb-c-bu... (of course, it may be slightly less efficient in boost charging, but since the 5V usb source has limited power, this may not be a concern in terms of component thermal limits etc).