Give the user the ability to retain the units while performing a "Save As"".
In Creo Parametric with a collaboration extension, the "save as" command will change the units to metric regardless of the original models units.
For example : I have an inch based part file in Creo and perform a "Save As" to a SolidWorks part file. When you open the part file in SolidWorks, the part is metric. The user has no control over this behavior.