I once heard that if you switch hands when the violin, guitar or any other instrument that each hand has a separate task, it enhances your technical capabilities in music, general technique, and is good for your brain, is that so?
The only times I find myself doing this is when, as a teacher, I need to remember how it was to be a beginner. I don't think this is a particularly bad idea but I reckon there's much more useful ways to spend your practice time.
As a side-note:
This is just my opinion but I never really understood why would people play guitar left handed. The left hand is actually the one that does most of the work so lefties benefits from playing right-handed guitars.