Sharing files (layers) with other architects/offices

[Anonymous]

I'm looking for suggestions how to address the following scenario: 

I would like to provide a limited service to various architects in the form of: creating/modifying or enhancing a single layer of their design - A good example will be the electrical layer of the house.

I would like to simple develop a procedure that will make their life easy to “export” only the relevant portion of the drawing to me, and “import” it back after I made the changes or created the new layer.  

I’m also aware of the reality that that different offices/architects are using different programs (AutoCAD 2011, AutoCAD Architecture 2011, Revit 2011 and Revit Architecture 2011) so I’m not sure there is a single solution for ALL products and versions therefore I might need to apply different strategies.

Your elaborate suggestions are very welcome.

[ToanDN]

Why re-inventing the wheel?  Use their drawings as background XREFs to draw your stuff on.  Send them your drawings to XREF into theirs.