". Look hard at your bike and gear.
2. Make a list of things that can go wrong that you could fix.
3. Make a list of the tools needed to do those tasks.
4. Find a tool or tools that can most efficiently do those tasks.
4a. Determine if anything can easily be replaced to eliminate excess tools (such as replacing Hex head bolts with Allen bolts, so you need only carry one kind of wrench)
5. Shop for a multitool that accomplishes some or most of what you can do for the bike.

Your advice is good as far as it goes but I'd suggest looking at the bike with an eye to reducing the number of tools you have to carry before the ride. Upgrade equipment to modern stuff where you can. For example, replace a threaded headset with a threadless (if possible). Replace square taper cranks with external bottom bracket cranks (XT trekking cranks are very cheap...$125). Replace cone and cup hubs with cassette bearing hubs. Although I still carry this tool kit while touring"

Looks a lot like my list from a while back, that is what I do. 4a is what you are refering to. Every choice
on the bike should partly revolve around making it easy to repair with as few allen keys as possible.

The biggest tool I have carried was a pedal wrench of medium serious design since the train I was using for my return trip required I remove the pedals.