Multiple Light Sources

Recently, I read Cesiumjs blog about deferred shading. Could you share more about the support of light and shadow?

1 As far as I know, due to the visual quality and performance compared to game engines and PC, some Chinese GIS teams try to use Unreal engine as the rendering module, then, they use the cloud rendering framework. In this way, they can avoid using WebGL. Some developers hold negative attitudes towards the future of WebGL(compute shader), WebGPU, WebAssembly, and the limitation of computation capacity in Browser. This is a possible way for web 3D application.

2 There are several ways to support multiple light sources: an extension of the current rendering module, deferred shading or path tracing.

My questions are:
1 Is it important to support multiple light sources in Cesium? If it is, which way do you prefer to choose?
2 Is it possible to use the unreal engine instead of the rendering module? For example, Cesium can provide a C++ version, focus on terrain and 3D Tiles such as performance && precision, and throw the rendering engine part to a third part library.
3 Personally,I want to know how Cesium thinks about path tracing, is it a possible orientation for Cesium to provide a career in the future?

Thank you very much for your suggestions.