Well, it doesn't seems to me as something impossible. I thought it could be like a texture applied on a polygonal shape. You could export and replace the texture anytime in any 3d soft till all the feather and levels are just modifications and not baked down into pixels.
You say such approach could work with Adobe /Corel soft? I have just downloaded Illustrator trial but looks like it also rasterizes all non-destructive editing down to pixels during export while I expected It could bring bitmaps as "smart objects" to Photoshop at least. And Illustrator is also 8 bit only as much as I know.
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