These are some great ideas, especially the simple ones like bringing a garbage bag. That’s something so easy and cheap that it’s easy to forget entirely, but as you say, it can make a huge difference in the right circumstances. It’s also good that you discuss some minor bike repairs. That’s another thing that can salvage or destroy your ride. You want to be as prepared as possible for the best possible experience.
All multi-tools are not created equal, but most with a plethora of features will get plenty of the jobs done. I personally like, and use often, the Lezyne RAP-21 LED tool, which will run you around $30. I like it because not only is it a high quality construction, but it has just about everything you’ll need, plus a sweet mini light. This will give you a chain breaker, spoke wrench, disc brake wedge, and all the most often used Allen keys and drivers. We’re talking a decent number of tools for 1/4 of what they would cost buying them separately.
A plastic garbage bag, or $2 disposable poncho: Just in case of an unexpected downpour or getting caught out after dark. More than once, I’ve gone for a ride on a beautiful day with a perfect forecast, not taken a jacket and had the weather go south on me. Being able to cover up can mean the difference between just mild discomfort or a freezing cold, shivering ride home!
A good patch will stick to your tube enough to keep air from leaking out. A great patch will act like a second skin and actually strengthen the tube where it’s applied, flexing and stretching with the tire. After 36 hours of testing, our official endorsement goes to the Rema TT 02 Touring Repair Kit. Its patches do everything other patches do, just better. The edge of the patch is also ruffled, which provides more edge surface area to bond—that’s a good thing.
Modern bottom brackets use a sealed bearing type construction that keeps water and debris locked out, so they seldom go wrong. Maintenance is impossible so they need replacing when they do wear out. Older style cup bottom brackets need to be re-greased every now and again, and occasionally will need to have their bearings replaced. There are a lot more teeth on the chainring cogs than those on the rear cassette, so need changing less regularly. Cranks usually a solid one piece construction so there is not much to go wrong.