External terrain renderer

Hi

I have been using Unity's terrain system to render paged terrains that are loaded asynchronously. Terrains are generated in Worldmachine 2 and look fantastic. Terrain scenes are saved as assetbundles. However a 50km by 50km patch results in about 120 MB of data. My app is actually a flight simulator for android. It already integrates JSBSIM flight dynamics model for simulation.

I was hoping if I could procedurally generate planetary scale terrain like this from C++ plugin that would generate a continuous LOD mesh and render it externally using OpenGL (though I have little OpenGL knowledge). I've tried running libnoise in a separate thread to generate heighmaps but assigning it to Unity terrain results in a momentary glitch. So I decided to render it externally. My questions are -

1) I know how UnityRenderEvent works on desktop but there is no explanation on how to do it from mobile. Do we need to call native render functions directly from a Camera's OnPreRender/OnPostRender ? And how?

2) How will I create shaders for that mesh.

3) How will render queue be defined for this native mesh? or is render queues a Unity specific thing.

4) Are render settings like fog set to OpenGL ES context by Unity or do I have to set them manually from plugin.

5) Is this all even possible or is there a simpler way of doing this?

Thanks a lot