Yes, the point you are clarifying is that a Revo map won't cause any damage when written over the manufacturers map (which should be common practice, as no one would be able to do flash re-mapping 
).
My area of caution is from the reciprocal angle. Are the manufacturers revised/updated maps able to cope ONLY with OEM maps, or are they able to also cope with overwriting third party maps, such as Revo? I personally doubt VW would be able, nor have the inclination to assess every third party map available, and create their own updates to cope with such scenarios. Hence the very real need to be able to switch back to an OEM map before any main dealer updates.
....Exactly! Not only does switching to stock then provide a known datum for the VW technicians to work from - for the car's and hence your benefit - but it also gives you peace of mind.
To the best of my knowledge I am confident that VW do
NOT create their updates with third party tuners in mind. This is supported by the fact that VW supply Revo (and possibly some others I don't know about?) with their updates soon after the VW dealer recieves them, with the intention of helping the tuner to revise their remap software accordingly.
There's simply no good reason to hide a remap from your dealer is there [Thinking of posts in another thread in this forum!]
