I am pretty sure you will not need D3D's render script, it looks like a straight render easily done in Poser's native FFrender engine.  And also no need for IDL.   Raytracing and cast shadows should be ticked on unless otherwise instructed.  Pixel sampling can be maintained at 3-4 pixels, anything higher will just increase render time. 

I am confused by the HDRI lighting.  Will other parties be providing HDRI images for your lighting?  It sounds light a typical IBL light for ambiant, global illumination.  But you lose that if you delete all your light sets from your scene.  I would be a better elaboration about that aspect of your workflow.  Also, IIRC, Poser does not support alpha masking.

I am not knowledgeable in animation just yet to confidently instruct you what is correct or wrong in the workflow.