The main question for this thread remains who the Enphase / ISO standards friendly OEMs will be. With Tesla saying they'll allow it now, maybe others will get onboard, but the risk is that they wall themselves off.
It should be possible for a vehicle’s built-in inverter/charger, the EVSE, and the MID to all cooperate even if all three are from different vendors, but this is not a thing.
If you have a Ford EV and a SunRun house, then it supposedly has worked for a few years now. (But that's just vehicle to home charging, not the "V2H" standard.)
Most recent teslas support 20amp at 120v output via official $100 cable adapter. Some other cars support about 20amps too, eg RivianR2. While it falls short of desirable amperage the car manufactures can bridge the gap if they wanted to. Even now I can run the bare minimum of workloads - a full size fridge, a small AC or Microwave, LED lights, and phone chargers.
Sure you can set a loftier goal and spend tens of thousands of dollars and countless hours solving it. Most people won’t though.
Today I could plug in a car that gives off 20amp into the same inlet, it would limit how much load it can carry, but I could stay below 2.4 kw if needed. Why wouldn’t that work?
In any case, serious V2H should support much more than 2kW. An EV with a charger with less than 6kW capacity is almost unheard of. Two EVs should be able to supply twice the current. All that’s technically needed is an charger that is physically capable of operating as an inverter (which I believe adds little cost), some way to derive a neutral (the usual solution is a relay and an autotransformer, again not particularly expensive), and the control logic to convince all of the above to actually operate in this mode.