Try to move Viewer to Modules.

[mrEuler]

Not sure how it will look like.. But let's think about it.
Viewer -> AbstractModule
|---> PerspectiveCamera is instance
|---> WebGLRenderer is instance
|---> Scene is instance

Or we can divide viewer in to several pieces:

WebGLModule -> WebGLRenderer
PerspectiveCameraModule -> PerspectiveCamera
Scene is always in ModulesProcessor as main root Object3D

Any thoughts? 🤔