Multiple UVs in Rhino are being supported by Thea.
The most important thing to have in mind, is that UV Channels in Rhino start from 1, while Thea Render starts from 0.

How to use Rhino UVs with Thea Materials:
Rhino UV1 = Thea UV0,
Rhino UV2 = Thea UV1, etc.

Having this in mind, you can assign different UV Mappings for every Texture Channel of a Thea Material.

The following image has been created using Multiple UVs.

Image 1: Created using Multiple UVs.

Anatomy of the scene:
UV Channel #1 (Brick): Unwrapped the model with the ‘unwrap’ command.
UV Channel #2 (Graffiti): Applied Planar Mapping.

Anatomy of the Material:
The material contains two (2) stacked Basic Layers. The Bottom material is the Brick and on top of that we have created the Graffiti.

A representation of how the two (2) Basic Layers look like.

Image 2: Basic Layers Representation

Brick Material: All the textures use the UV0 Channel (UV1 in Rhino).
Graffiti Material: The Diffuse Texture uses UV1 Channel (UV2 in Rhino) while Layer Weight & Bump use UV0 Channel.
– Layer Weight (Graffiti Layer): Using the Texture Layer, we mixed the Bump Texture with an Alpha map.

This is how the material looks like inside the Material Lab.

Image 3: The Final Material inside Thea Material Lab.