Working in the energy space, I don't know why a driver would want this. It's the same problem with V2G schemes. It means that you could decide on a whim to go for a drive, walk out to your car, and find that it has no charge.
I saw some pundit conversations about Battery Day recently. There's some speculation that a 'million mile battery' may be coming due to union of a few different complementary improvements to the battery design and manufacture.
If your battery can survive four times as many discharge cycles as the drive train, hooking back into the grid isn't so bad as long as your car doesn't conk out 10 miles shy of Grandma's house.
If you know your going to be parked at the office for the most part for 8 hours a day, then you'd probably be ok putting your car in opportunistic mode as long as you have enough for your commute.
The car can also track your driving patterns and manage all of this seamlessly. Having worked at a gas station and seeing how people swarm my station when gas was $0.10/litre less than the surrounding stations because we didn't update fast enough, I think there will be plenty of price chasers for these modes.
The anxious / I drive for recreation types / road trippers can pay extra to stay topped up all the time.