As of earlier this year, MMC did offer Stage 1 and 2 - my upgrade was done at the factory. What they will not do is dyno-tune - they only reflash the ECU. It is cheaper to have this done while the vehicle is being built as there is no need to remove stock exhausts.
I like that shade of green/blue in the video.
And what does this lovely kit cost ? And most importantly is it available for an EU4 (last time i checked it wasn't)
When I visited the Factory May this year it was one of the many questions I had for the sales manager. I still have the Excel file I created and he filled with his replies

It is written "It will invalidate your warranty", so I disregarded this matter since. Maybe as Osten says, it's not good for EU4? I don't know, but it sounds shady...