As a layperson, my own views overlap with @gorillapaws and @vimead1. I think they should place a lot of weight on a “defensive defense” strategy like what’s described here for China and its neighbors: https://www.tandfonline.com/doi/full/10.1080/0163660X.2019.1693103.
It seems to me like the conditions in Germany are less conducive to a “defensive defense” strategy than they are for China and its neighbors. But I still think it makes sense. We don’t want Germany to repeat the mistakes made by NATO in Europe and the US allies in the western Pacific, where so much of their defense buildup is based on the threat of a counterattack into enemy territory.
I understand that there is a place for “aggressive” things like missile defense, intermediate-range missiles, aircraft carriers, landing craft, and whatnot, but I think the US has relied on that stuff too much and it has scared countries like Russia and China. As a layperson, I think Germany should be willing to pay extra (and even take some military risk) in order to keep its strategy as “defensive” as possible.
In the age of the supply chain attack, I think they should also avoid relying too much on highly complicated equipment, and avoid building something new when something old is 90% as good.