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The answer given was : "theoreticaly All functionality depending on how the third party wrote his own plugin"

"I'd still have to use DS, right?"

From the description I would say yes
it would likely be an additional Export option from Daz studio
ex save as FBX ,Colladda, "DSON"

To me it sounds like they are extending the functionality of their dsf format to full scenes, not only their characters. They could easily have some success with it, because it is so simple (in my personal undiscussible opinion at least). Because when you look at the fileformats that work best for exchange of data between applications, you find obj, bvh, mdd and tga formats which have the common property of being dead simple, and less of pz3, collada, 3ds and max files, with each of them undoubtly being more powerfull than all the simple formats put together, but simply could not make it into big world of import/export formats because of their complexity. IMO especially game developers like simple formats (probably because they rather spend their time testing their games instead of reading specifications :-)