What's typical A-hr capacity of the batteries?
Indeed, that potential and having to have both the time and location to ensure could go somewhere (and get back) make the whole concept totally unworkable for anything except the niche commuting market or the like.
Of course, there's a large niche of day-commuters so they would have a place. If one can do without the alternate general-purpose, on-demand need entirely, I suppose one might even be able to make a reasonable cost basis of not being too much of a hit, but if, like with wind and solar until there's sufficient grid movement to avoid some of it, there still has to be that standby reserve to pick up the demand when not there or lose grid reliability. Likewise, have to still have the ICE option too or lose the flexibility.