It is no problem changing lenses in midroll! Just avoid pointing the camera, with the lens off directly into the sun - just tilt it down.
However, the caveat is most disasters happen when you change lenses! Suddenly you really need three hands, camerabody in one, old lens in the other and new lens ?! I have on occasion dropped cameras, but not that often - I have dropped lenses more frequently, particularly if you change lenses in a crowd.
With the Leica baseplate and reloading, you can always hold the baseplate in your teeth - cant really do that with a Noctilux or Summicron 90 - unless a/ your bite is much worse than your bark and b/ your dentalplan covers more than most do.