[namibj]

Actually, the power density of a charger shouldn't be an issue for this. You can get very dense systems if you're willing to cool them appropriately (the frequencies you can use thanks to modern GaN and SiC transistors allow for very compact inductors and make switched capacitor converters feasible for mains voltages).

10 kW/kg is not even exotic anymore, and I doubt you'd want to charge at more than 100 kW with an on-board charger, anyways.