None of the members of this government department want a bespoke system, they want to use tools they are familiar with but due to the firewall rules this isn't possible.
Spoken from experience, this includes things like Anaconda in orgs where devs can’t use just any Python packages, or scripts from the internet copied and pasted into files because the firewall blocks git cloning. One could even consider AWS as a platform for devs to get around InfoSec red tape and have some semblance of control. The goal as a dev here is to fight the fewest fights to make tools available, by getting access to the biggest “bundles” of tooling they can.
In such organizations, there is either no concept of cost/benefit of overly restrictive firewall rules, etc, or the culture is such that the security team has become entrenched and unquestionable.
When the only tool you have is a hammer, everything by necessity becomes a nail.
The proper solution is just to fix their firewall. The interim hack is what you've identified, do some sort of gateway.
Unfortunately my bosses are non-technical and think we can simply copy google data studio with 1.5 guys and 12 months.
Understandably I am seeking new employment.
It's very rigid and slow :(