every change pisses off someone. it only has to be announced well in advance, so that nobody gets screwed up by last minute adjustments.
should be pretty well announce before ... Because to train a SF could take years, and when you start a lot with defence and another one maybe with JS, he will reach the other one level easy.
And actually there are also good SF, sometimes they go from a C trainer to a Guard trainer in their development, sometimes teams change there training good etc.
I don't see the need for a change. Which is totally impossible when i understand what you write, so i had really hard problems to understand you.