if you have to switch in the last moment just switch off everything and fly it manually raw data, basic flying is sometimes still required and actually quite a lot of fun.
Agree. The problem is that surprisingly few pilots are competent to do this because in all their FMS lives, full use of all available automation has been drilled into them and they lack both the self confidence and the situational awareness to keep their hand in during sunny weather.
As for quickly switching from automatics and all its pretty colours on the MAP mode to basic raw data hand flying all in the space of a few seconds, well there are some who argue for an immediate go-around and go into a nearby holding pattern in order to perform an extensive brief on how to set up the raw data. I kid you not..