3D Objects, Dynamic Blocks, Block Attributes, etc....All of these objects have hidden or unseen data and they can all reside in a single drawing. My question is this: How much of that "hidden data" effects the actual size of the finished drawing? And is there a way to efficiently remove or purge this redundant data out of your drawing prior to delivery?
Everything that is part of the drawing affects the size of the drawing.
If you have blocks that have invisible attributes and you want to get rid of those, redefine the block without those attributes.
I'm not sure what hidden data would be attached to a dynamic block - other than attributes - unless you have Object Data created with AutoCAD Map or Extended Entity Data. I would have to inspect your drawing for that. If you mean the Dynamic Blocks have their parameters and actions, redefine the block without them, but the usefulness of the block goes down.
Regarding 3d objects, there are many types. If you have meshes, you can reduce the mesh density. I'm no expert on these types of objects so I can't give any more advice than that.