No,it's not possible,for now only models can be extracted,but there aren't custom models for DR3 yet,and even if there were we also would need to figure out collison,which possibly will be really hard.
Like Ben said we can't we aren't even that far in the engine's research to see what can be done. Plus we never figured out how to import custom maps to DR2 and OTR since no one could make tools for it and such. So to sadly cut it short, no we can't for DR3 yet or previous titles. Not till research is done and a person with good knowledge can make a script or program to help us achieve this.