And it quite possibly creates a huge risk for the company in the longer term, there is only one person who knows how that all works.

Honestly not super sure if that is more of a risk than it was pre-llm.

As part of the aquisition I got access to their previous codebase which was some sort of incomprehensible PHP monolith, with the persons who wrote that code long gone. Thanks to LLMs I was actually able to extract the core useful concepts (again, sufficiently deep domain knowledge that I knew exactly what to look for). Without LLMs i would have probably extracted the absolute minimum and let the rest rot.

There is no reason a dev of comparable skill and domain knowledge would not be able to do that for what I built here.