To be honest, motorcycles tend to be very reliable these days. Thanks to improvements like electronic ignition and better electrical connectors, sitting hopeless by the side of the road has become less a part of motorcycling life than it was a decade or so ago.
But there are still a few perils that can leave you stranded. However, forewarned is forearmed, so you should take action against there mini-disasters. A session in the workshop, slipping a few choice components under you seat, should see you immune to many breakdowns!
An underseat treasure trove of anti-disaster goodies is a genius move. It'll depend on how much space you have of course, but at the very least, try and include a puncture repair kit, with come co2 canisters. An 2,000 THB emergency money will guard against those 'came out without the wallet and am 200km from home' moments. The motorcycle's tool kit is worth keeping in place, but you might want to dump some of the more useless items and replace with your own bits. Cable ties, lockwire and a small roll of tape can help patch up light accident damager enough to get you home, and a spring link for your chain could help if the chain breaks (although you'll probably have bigger worries). Finally, a spare headlight bulb, a ziplock bag of fuses and a length of wire will help sort any electrical miseries. Add in an energy bar too, for those 'sat waiting for hours before help came around' scenarios. On the motorcycle itself, regular maintenance will prevent most potential breakdowns. If you're off on a round-the-world trip, you may want to consider cable-tying backup clutch and throttle cables alongside the ones on the motorcycle. Then if a cable snaps, it's a simple case of swapping the ends over. Getting into the throttle body end may still be a problem of course...
The things that will stop you moving after a crash are broken controls or holes in the engine. Fitting flip-up clutch and brake levers should keep them usable, or slip replacements under the seat. Keep a small piece of two-part epoxy resin in your underseat emergency kit too: it might patch up a small hole in an engine case or radiator, although you'd want to make sure there's no grit inside the engine before you start her up again.