I've seen that you had discussions earlier about installing plugins for a specific theme. I would suggest to revisit this.

In general, pre-packaged Theme plugins are included in the installed theme already, but the are zipped and lie in the themes/{theme}/plugins directory.
It would make sense to unzip these plugins directly into the plugin directory.

To make this behaviour predictable and on purpose, we could extend the current configuration to define a series of strings/globs for identifying plugin-ZIPs to unpack:

"envato": { 
        "packages": {
            "envato/bridge": {
                "item-id": 7315054,
                "type": "wordpress-theme",
                "plugins": [
                    "bridge-core.zip",
                    "layerslider-***.zip"
                ]
            }
        }
    }