I'm not sure why you're being downvoted. All it takes is a simple weight sensor, couple your suggestion with an "overweight" LED to give the user some feedback and this becomes a non-issue.
Except if your weight sensor if the first thing that breaks when the machine gets old.
I think all this is completely over the head. Say what maybe 3 machines exploded? That's far below the "noise" you have in every thing, it is statistically irrelevant.
Also, side question: when I pay for a product like a baby stroller from a western company, which part of this money is spent on "law abiding", i.e. the verbose amount of warnings sticked everywhere and all the lawyers behind? I just bought one and this kind stroller tells me loudly I'm stupid from every side of it. I had a Japanese stroller before: cheaper, lighter, just better for kids and parents in every respect, and a just a brief non-liability warning. If I put 4 ten year old fat kid is will break, OBviously. That would be my fault.
