I have been thinking this already.
Think about a apartment building which has 50 cars every night parked.
When they are all EV's it is a yuge capacity of electricity.
The building could have solar panels on the roof, and charge all cars during daytime, and then during nights the cars could give back providing electricity to the building or families needs. Also those cars who stand there longer, like week for example, could work as a storage and sell electricity it to other cars if wanted. so basically cars would provide a storage for electricity for common use if solars would create over use

Now, imagine recharging at a highway rapid charger which is going to be relatively expensive and someone just taking that energy from you. Not very funny. They would have to give it back, in full, covering any losses, free of charge and pay on top in some form (e.g. reduced distribution tariff) to motivate me to allow it in the first place.

"For example, if you arrived home from work and parked your car overnight, some energy stored in the high-voltage battery could be transferred to the grid. [...] You could then recharge your car at a lower cost during off-peak hours."

That doesn't make much sense, does it. Electricity is the cheapest at night because there is little demand. Especially when you have many windfarms in the mix which produce whether you need it or not. The price can even get negative where you essentially get paid for being so kind and consuming some of the dreadful stuff. Selling electricity at night is a dumb idea. And when would you suggest I recharge then? Which off-peak hours you speak of that are even cheaper?

First of all, your distributor needs to support this. Where I come from, it has to be part of your contract. You can't just supply electricity to a grid. And in this case, you're probably talking about distributor controlling the flow - taking energy when they need it. The bigger problem is that you're not paying just for electricity, you're also paying for distribution. Which makes the economy of selling electricity (which was purchased) back to the grid very challenging. It would require a special tariff where you don't get charged for distribution as you're rendering a service to them. More than that, they should pay you for this service. As your property will incur wear and there will be energy losses. Otherwise, you'd be running a charity.

Another complication is that for this to work at peak hours, your car would ideally need to know when you want to use it again. You don't want to get in your car and find out it's at 50 % when you were expecting 80 %. And you don't want to be using that top portion of battery capacity unless you get well paid. Of course, at scale, perhaps just 5 % would be enough for them, across millions of cars, minimizing this issue. Peak hours are during the day which means that the car has to be connected at that time and the parking lot or wherever the car is must facilitate this which will complicate financial compensation.

Now, vehicle-to-home can be about charging during the day and supplying it back at night - if you have solar panels as sun doesn't shine at night. It could allow you to significantly reduce the size of your house battery. But that requires your car to be plugged in at your house during the day.

"V2G also reduces operational costs and decreases our reliance on fossil fuels."

How so? Can you explain your idea? Whose operational costs?