Your logic seems to be broken: IF you have an EV car with something like 50-100kWh and you know that either you only travel short distance in such a week OR even stay at home, you can provide load support just by having the bi-directional loading controller checking the frequency of the power grid.

It could just stabilize it out of the box with minimal technical requirements.

It might even be easy in this case toa lert EV owners to do one or two plug ons and offs manually for the grid.

Loading the EVs slowly before the weather or when the other load is gone, could also help supporting the peak usage.