My first suspicion would be the battery itself going bad. Since you have 14v to it while riding, the first-glance at the charging system would indicate that it is ok.
Yes, you can take apart an ignition switch if you are very patient and don't need it to look perfect. I'm not very patient so when I do it, it works, but looks buggered up.
However, if you end up having low voltage to the battery, it won't be the ignition switch causing it. Voltage drops at the ignition switch would cause the charging at the battery to be too high.
One failure mode of the now nearly 40 year old reg/rec is that it can initially show 14v at the battery, but during a long ride the output to the battery slowly drops down to nothing. I've seen at least two fail this way on Kz550's. The way to tell is to somehow mount a voltmeter on the tank and connect it to the battery. Initially you will get 14v and as you ride it will slowly drop to 12v.
If that's what you have, then you can get a Ninja 250 or 500 reg/rec from the early 2000's for like $10. They work well but will require splicing wires since the connector is different.