> every time they needed support for a new model and had to update llama.cpp, an old model would break and one of their partners would go ape on them. They said it happened more than once, but one particular case (wish I could remember what it was) was so bad they felt they had no choice but to reimplement. It's the lowest risk strategy.

A much lower risk strategy would be using multiple versions of llama-server to keep supporting old models that would break on newer llama.cpp versions.