This is the tool Wilko used to update new weapons
As the standalone already supports all base game weapons
This tool can be used to add support for custom weapons

Requires:
Microsoft .Net Framework 4.5

Instructions:

Open GoonModWeaponCustomizerTool

To add custom weapon support select mod_overrides folder as your extract folder

Create a folder and set it as your mod_overrides folder

Then click process once both folder are selected

It should take less than 5 minutes to complete

Source Code
https://github.com/JamesWilko/GoonModWeaponCustomizerTool