You are spot on. We have several bicycles in my extended family and I have the tools to repair all of it, but when we bought or built the bikes we looked for th

You are spot on. We have several bicycles in my extended family and I have the tools to repair all of it, but when we bought or built the bikes we looked for the widest compatibility possible of the spare parts: 2 BB types, 2 chain types, 2 fork and bearing types and 4 wheel sizes for ~ 10 bikes. The only "rare" tools are a Shimano Hollowtech 2 wrench and the "square BB" one, the rest are common tools most people have in the house.