Face Masking Overlay : Controlling bounding box color and fill opacity from analytics plugin

Subject: Controlling bounding box color and fill opacity from analytics plugin

We are building a face-blur analytics plugin using the 6.1.2 server plugin SDK. Face detection works and bounding boxes appear in the client. We want to set the bounding box to a solid filled rectangle (to act as a privacy mask) rather than an outline.

What we have tried:

IObjectMetadata / ObjectMetadata — no color or fill properties
Object type manifest (typeLibrary) — only id, name, icon, flags, attributes
NX Client camera settings — no per-object-type color/opacity control visible
Questions:

Is there any SDK API (manifest field, metadata property, or attribute) to set the bounding box color and fill opacity per object type or per detection, from plugin code?
If not in the plugin SDK, is it possible via the NX VMS REST API to configure the rendering style of a specific object type at runtime?
Is there a supported mechanism to have the analytics plugin modify video pixels (e.g. apply Gaussian blur to the face region) that are then displayed by the server, rather than just producing metadata overlays?