How to edit files/make mod that edits arsenal contents for a faction?

I run a small GM server for a few friends and we play as the British using the British forces mod (Brilliant mod for 80's Brits).

However, to gain access to modern day British weapons using Phoenix Studios Weapons (Everything Phoenix do is brilliant), I as GM need to add an Arsenal for a second different British Faction it seems.

To then get access to modern British gear and uniforms using Prontos Brit Kit (again, brilliant), I add another US Arsenal.

This makes gearing up a tedious process sifting through various gear split between three different arsenals, one of which has 20 pages of US stuff before getting to the British stuff.

Is there a way to condense all the stuff we want into one arsenal, and hide/remove the stuff we don't?

There do seem to be some modern day British faction mods that would probably solve this issue, but they use the same dependency which no longer seems to be available to download.