I imagine that using one EV to recharge another EV could be practical for example you are stranded somewhere, a little bit like a jump start between two ICE car, but for an everyday usage this would be quite overwhelming. Why not getting an extra PoweWall, or making yourself one, in addition to your own solar installation. There are a lot of example of DYU EV charging station on Youtube using refurbished batteries from car junkyards. Here are some examples. These DIY Powerwall Hobbyists Are Building Their Own Home Battery Systems DIY Powerwall Builders Are Using Recycled Laptop Batteries to Power Their Homes Can't Wait For (Or Afford) A Tesla Powerwall? Why Not Build Your Own For $300?