70 GWh of battery storage would have kept the lights on for an extra 2 hours during this event - assuming the batteries themselves aren't affected by temperature. While battery storage might be nice to increase the capacity factor of a solar or wind farm it isn't going to make a difference in an event like this where a weather system moves in for a week.
The current grid took a looot longer than 2-4 years to build, and that 17GW/50GWh is just 2-4 years of replacement equipment at the very beginning of a transition. So I'm not sure why this amount of batteries needs to power the entire grid, or how that's a helpful or even interesting comparison.
