A few years later I found myself in a similar position as I led groups of paying customers, and I had to be able to fix just about anything at the side of the road. What goes into a toolkit takes a great deal of thought and planning, often forgetting a simple tool can leave you stranded. Lastly the number of tools you carry can be greatly reduced by careful selection of components on your bike. The first thing to decide is what may go wrong with your bike, but which cannot or doesn't need to be fixed at the side of the road. For example frame failures need special tools and equipment.
Bottom brackets require heavy tools to fix or adjust.
I fit a sealed annular bearing type. This needs no adjustment and when it fails it generally gives plenty of warning, creaking noises, free play etc. It will go on for days like this, giving you chance to get a replacement, which are a standard fit anyway. The same generally goes for headsets, choose one that can be adjusted with an allen key. Next you need to look at what is likely to go wrong and prepare for it.