From BlenderWiki

7. Transparency

This is subject to high interest.
Transparent surfaces should be put into a second pass to render them in front of opaque geometry.
But we have problems when multiple transparent object overlaps.
We can't avoid every problem but we could at least let the user have a mean to give object priority for this sort order. Plus we should sort them by distance to the camera by default.

We could also for completeness introduce a Modulate/Multiply Blend mode that darkens the scene. This would mimic the behaviour of the transparent shader in Cycles. https://www.opengl.org/discussion_boards/showthread.php/144760-Blending-Mode?p=1038945&viewfull=1#post1038945

8. Post drawing

We have to save the pre tonemaped HDR color buffer for the SSR of the next frame.

Then Use a tonemapper operator (we can use OIIO for that) to map HDR to LDR.

Then pass the frame to the Compositor.

And all eye candy effect will be handle there but that's not the scope of PBR itself. Bloom and camera motion blur should be easy to do.