Boxers or briefs? Depends!
We all have opinions so here is mine. Some of the things you can do in development should NOT be kept when you move into production. For instance, in-context relationships to other parts or assembly states is great for developing the design, but they should, in my opinion, be broken and replaced with a part that is completely defined by its own dimensions and constraints when moving that part into production. Configurations are also wonderful for development and should be separated into separate parts when going to production. However, there are good reasons for exceptions to this for configurations. Keep in mind that configurations are not separately controlled with PDM. PDM only controls revisions of the part file.
A mirrored part is something different and you really have take into consideration its use. In the aircraft industry mirrored parts are quite common and often pretty involved so making a mirrored detailed drawing would have been a pain. Necessity is the mother of invention so they developed a simple means to deal with mirrored parts. Mirrored parts had different dash number series. The parent part might have a part number such as 74A123456-1009. The drawing for that part would detail that part and then show an image of the mirrored part with a view label of "-2009 MIRRORED PART". This worked for two reasons, 1) because it was well communicated throughout the company and industry so everyone understood it and knew how to work with it, and 2) because the mirrored part was truly a mirror, i.e., whatever happened to one part also happened to its mirror. Any revisions to the part, by definition, also happened to its mirror. If this relationship could not be maintained then the parts were separated into independent part numbers with no association to each other.
So, if you want to make mirrored parts that are true mirrors of each other it would make sense to follow the lead of the aircraft industry and make sure it is well understood how to deal with them. Otherwise you should keep them separate.
If the parts are not too complex it would likely be better to model a mirrored part using the same features as the original. FeatureWorks is a very handy tool (and I would also recommend exporting as Parasolid instead of other formats), but FeatureWorks cannot see how the part was modeled, as Eric said, and therefore will miss the design intent. Sure, you might get a fully constrained model, but if the dimensions automatically dumped into the drawing are different then what's the point.
If the reasoning behind the restrictions on mirrored parts is that they need their own drawings then I would suggest keeping the mirrored part itself, pulling it onto a drawing and manually dimensioning in a mirrored fashion to the original part. This way there is no export/FeatureWorks issue and it is pretty simple to copy duplicate the dimensions of the original drawing.
On another note, if your expert cannot adequately explain his reasoning then he is just an arrogant ash. Sound reason and good justification should rule, not someone's opinion. But then, that's just my opinion.
- - -Updraft