My gripe about WAR is that it does not punish for strikeouts. I think they are usually the worst batting outcome. Yes, it can be argued that a 12-pitch K is valuable because it tires a pitcher, but the game is still measured by runs scored. The 100-pitch max dates from Paul Richards, who maxed his young pitchers (were they nicknamed the "baby bulls"? Milt Pappas was the first and most famous). It's not obvious that 100 pitches, or 90, or 115 pitches should be the maximum. Seems arbitrary, something like pulling a starting pitcher for Drew Storen with two outs in the ninth if the starter has just walked someone and you "always" go to a closer with one on and two out on the ninth
OPS is interesting, but there should be a measure that counts a K as more than a simple out.
Many people, such as Boswell, claim that BAPIP should hover around .300. I think he used it to argue that Espinosa would show better as son as his BAPIP rose to "normal".
I happened to look up a few players, and my old hero, Harmon Killebrew, never managed a BAPIP of .300. In his first real season, 1959, his BAPIP was about .230, although he tied Mickey Mantle for AL home run champ with 42. Every one of us kids thought that our Killer would someday make the Hall of Fame. Killebrew was rushed back to the majors before he learned to field...the Nats were that desperate and his hitting was that good.
Maybe Killebrew is just a quirk. Frank Howard had a higher BAPIP before Ted Williams taught him "the science of hitting". His BAPIP in 1969 was about .285, even though his BA was about .295. If I could pick players from Washington's past, I would pick Harmon and Hondo, among others. Of the players I would pick, on what I've read, I would pick Sam Rice for CF. His career BAPIP was about .330. That was not luck: he was that good, and so said Bucky Harris, Ty Cobb, and Shirley Povich. I would also pick Cecil Travis, the best player never to get a single vote for the HoF. His career BAPIP was also .330, and it was no fluke. He joined the Army, served throughout WW2, from his feet during the Battle of the Bulge. In 1941, he was about 28, hit .359 (second to Ted Williams, who hit over .400) with a BAPIP of .366. He was getting better, pulling the ball more often. Discounting 1945 - 47, when he played on damaged feet, which cost him his balance at the plate and his speed, his career BAPIP would be even higher. (Yes, from what I've heard and read, Cecil Travis was a better SS than Derek Jeter).
What about xFIP? Agreed, it would be nice to measure a pitcher without considering the fielders, but that should over-value strikeout pitchers. Extreme example would be Strassburg compared to Zimmermann or Fister. Strassburg has spectacular stuff and a great ratio of K's to BB's, but Zimmermann and Fister are more effective pitchers.