The veteran coach of the single most successful HS team in our area just switched to coaching the softball team at his school. His teams have won many league championships over the last 10 years, along with three sectional championships, including 2 straight (sectionals is as as high as it goes in California, since, unfortunately, we don't do a state baseball championship). He has also sent a constant flood of players onto D1 programs and even a few to MiLB and MLB. Says be's burned out after 20 years of coaching baseball.
Don't know of many precedents for this sort of thing -- i.e. a hugely successful baseball coach switching to softball.