Just a general suggestion here, as a first step, do some diagrams of your environment. Start with a general diagram and work from the top down to more specifics. Consider what goes into like buckets of use cases, and where use cases are different. All this vlan & firewall talk is downstream of design intent.

There is no appeasing these loons. The “Bro” IDS system had to change it’s name a few years back because…no one even knows.

https://en.wikipedia.org/wiki/Cargo_cult

Agile/Scrum, ISO 9001, ITIL, Six Sigma, CMMI, etc; it’s all cargo cults.