That's the answer, and lots of companies do it. If you're going to fire, fire quickly. One problem with that is the high cost of onboarding, which is (IMO) caused by HR making their own job security by pushing for long hiring processes. If you just spent 3 months searching for candidates and getting them at a desk, you don't want to spend another 3 months if that didn't work out. So you have to cut your hiring lead time to a more reasonable level first.