Elsewhere I read that V2G will not become standard until 2025
Having a 13amp plug (and idealy 110 volt) on cars/vans would be great for many people. A very clever design may be able to reuse the inverter that is used for the car's moter.The inverter would have to be outboard, it would make no sense having it on the car for many reasons
These are my thoughts as well. I was intending to buy my first EV this year to integrate with newly installed PV panels. I had looked at the Leaf as CHAdeMO already supports V2G protocols. However, the Leaf's passive battery cooling has put me off big time. Great as a commuting car, but problematic for a single car household wanting a vehicle for touring. Being retired with limited funds, this may be the last car I buy (I tend keep my cars until they fall apart). I believe that V2G could provide massive environmental benefits and I would not like to miss out on being able to contribute to this.Technically it is almost certain that most cars could support V2G via a software update, as it's just an extension of the communications protocol - the actual power hardware is just the contactor to connect the charge port to the battery, which it already does for charging. It's possible there might be some cases where, for example the hardware can't measure the current flow out of the battery to the charge port. There might also be some safety approvals & testing costs.
However there is little incentive for them to do any sort of retrofit so I can't see it happenning for any existing cars.
A lot of the software and hardware involved will have been bought in from subassembly manufacturers, so any upgrades would likely cost the manufacturer to deploy, both in licensing, and any integration work.