Hi eldiren, thanks for reaching out us.
With regard to your request, please consider that ProRender has been integrated by using a non-public API which among the different features also gives permits to integrate the renderer buffer with the viewport.
At the moment aside from the documentation about VideoPostData for non-interactive or semi-interactive rendering purposes and the approach seldom used of representing in a GeUserArea or via the SceneHook::Draw function the results of a renderer buffer, there are not yet examples showing how to integrate external renderers in Cinema 4D.
Best, R