Uh hard. First, maybe don't buy companies with bad technical debt, just start from scratch? And always prefer two experts to 10 juniors in the beginning even if you move more slowly at first. I don't know what would have worked well in that particular situation, but if I were to do it again and could influence the original team, I'd use Clojure. I believe the immutability and control of side effects would have been more of a benefit than types. That was where the real problems came from, dynamic ability to create out-of-sight side effects and alter data in unexpected ways all over the damn place. Clojure's immutability plus spec would have been way better.