Heh. What would be your favourite thoughts/combo here?
Sorry for not being clear on the code part. I assumed USD and the like would be the norm now. "Complex objects" is not really helpful in this context, though.
USD is fairly widely used. But it's not "code" in the sense that I mean it. It's (mostly) declarative (like HTML) so I lump it in with obj, fbx and gltf.
I am assuming code means "executable code" - I know the boundaries are fuzzy here and some file formats are Turing complete - but I guess what I'm saying is that I'm still not sure what you're asking!
Sorry for not being clear on the code part. I assumed USD and the like would be the norm now. "Complex objects" is not really helpful in this context, though.