Grid-scale batteries are not the solution. Residential solar combined with residential storage either through dedicated batteries (which can be repurposed old EV battery packs or tailor-made residential storage batteries) or electric cars which can feed power back into the home can help more here by limiting peak consumption when people come home from work/school and - given large enough batteries - when they get up and prepare to go to work/school. In the more northern regions the effect will be limited in the winter months due to the limited amount of daylight, the opposite is true in the summer months.

First sentence: I don't think these things are mutually exclusive. Agreed on the rest though!

One of the main advantages of battery storage, apart from decoupling production and consumption, is that it enables delocalization (and portability) of energy sources.

Therefore they will use stored hydrogen in the gas plants. The hydrogen will be electrolyzed using renewable energy when it's too much.

“current capacity” is indeed insufficient, but we’re talking about what ought to be in the future, not about what is in the present.

The technology to do that at reasonable cost does not exist and likely won't be developed in the near future.

The technology does exist. The bottleneck is how fast we can ramp up mining and production of key metals.

Extraction of key metals from batteries (ie.: recycling) does need to be developed further, but in terms of total capacity, that is a bigger future concern than a present one.

What's a reasonable cost? Wind and solar are pretty cheap, and you can spend quite a bit on technology that you only need a couple of weeks of the year without doubling the average price.

Lakes make for good batteries. Geography provided.