The question comes down to this: is it more cost-effective to buy chargers and mount them in one physical location (your house), or to buy those chargers and mount them in the car? In a public setting, such as the Superchargers, Tesla thinks it makes sense to mount a lot of chargers in one location. At home, though, you won't need the capacity nearly all of the time.
Charging at home, you rarely are in a tearing hurry. A 0%-100% SOC charge can be done in about 4.5 hours with twin chargers. Roadster owners report that even that rate is probably more than you'll ever need -- at home. Where you want extra speed is on road trips, but then having paid to install extra charging capacity at home doesn't help you.
So, short answer: 20kW of DC charging at home means you have installed 2 10kW chargers at home, plus one in your car. 20kW of AC charging at home means you have twin chargers on the car, which is two-thirds the cost PLUS you can charge at up to a 20kW rate on the road. @cattledog's idea, while technically feasible, is likely to be either needed or cost-effective.