Earlier quoted context omitted.
This is excellent advice but I would back up a few steps and do a few things before bringing in a freelancer team. Identify a part of this system that can work somewhat in isolation and is non-critical if at all possible. Then document the requirements for this part thoroughly. This allows you to: - Have something smaller for your new team to cut their teeth on. - Ensure you have collected all the diffuse domain know…
> This is difficult and time consuming so start now. A specific difficulty you are likely to face: Your expert employees are busy doing their jobs. Writing requirements means taking attention away from that work - a difficult proposition, especially if they have managers who will ask why their KPIs are slipping.
You need personal access to talk to the experts anytime some question comes up. This means 1-2 experts work part time as PMs more or less, which will impact their regular work.
Costly, but I don't trust any other way.