V2G i think will bring some issues in many countries.
if you own the car outright, then fair enough its a risk you take and manage.
But if you got the car on finance, and use V2G and dont have the intention to pay the balloon at the end knowing the number of charge cycles you have put through the battery - will the finance company be happy to pick up the cost for a battery replacement as techically mileage of the car may be within the allowed annual milage?
if you lease the car, this is even more of an issue as you who lease the car have 0 responsibilty after the lease expires, long as the car is under the mileage allowance and works.
Cheapest lease for MG4 is £250/month atm for 4yrs - for 64kwh battery; based on current octopus flux cheapest import rate of 20p/kwh and best export rate of 36.6p/kwh thats £10.6 worth of money each cycle (100% to 0%). assume you have facility to discharge at 22kw to the grid thats £300/month of income which offsets the lease but battery might start getting knackered in a couple of years. conservatively say you charge to 80% and discharge to 20% daily - thats £6.40/day...
i dont think the fiannce companies will be knee to pick up costs or let you generate income like that or maybe they are none the wiser....
current car finances of any sort will have small print saying you cant use the car for commerical work, maybe when V2G is a reality, similar sanction will be imposed??