That's very interesting!
But some questions - sorry - I am focussed on Terragen so far (maximum some really marginal wings3D, blender and Poseray knowledge)
Which program is rendering which part?
I some time ago had an idea that theoretically a body-posing-animation in Terragen could be possible, if there is a script that imports a sequence of different objects. But before (in my idea a sequence of - let's say 100-200) - object files must be exported from eg. blender.
I even don't know if loading a different obj file frame by frame for the same object is possible in Terragen. But I already could bring something similar to work with the image projection in my Helicopter rotor projection. So why not?
The other side is that posing and animating rigged objects is not that easy -- I needed 2 days just to pose a simple hand just holding something in it's fingers - only creating that object - not even animated!
(With Blender --- seems that eg. Maya is easier to use but 200 $ PER MONTH ??