This engine is not new - I'm not sure why people think it is. All of our 1M customers so far had 135i's tuned by us to 420 BHP and completed 30k miles plus without any issues - thats why they have come back to us with their 1M's.
Tuners all over the world including ourselves have been tuning the N54 to much higher power levels than the 1M with a map without any issues other than what is normal for this engine ie fuel pump.
I agree any customers tuning their cars should disclose this to their insurers and most do. In the UK at least it does not add a huge amount to the insurance premium.
As with anything in life there is risk - some people are ok with this and some aren't so I understand where you are coming from.