In the 3D environment, Inventor is build completely on the principle of reference other files within a file (parts and assemblies within other assemblies for example).
How ever one section where you don't have this possibility is within the 2D environment.
It would be very handy to be able to place or reference other idw files within another idw file, just like you place parts or assemblies in other assemblies.
Files would be far more manageable if you can reference the same idw drawing over and over again, instead of making new one (or copying the sheets) each time you need it in another drawing.