> Or put another way, if fuel goes up astronomically and people buy less of it, they will adjust its weight downwards, limiting the effects of its price increase on the headline inflation.

What problem do you see in that approach? That looks exactly like the expected behavior from the average consumer.

If your goal is to track the prices of goods and services actually consumed by the population, isn't it appropriate to lower the impact of goods and services that are consumed less by said population?