Hi crossroads
If you buy an older machine you should go first of all by the experience of the other users. This means what is a good brand, what is about the spare parts, how to get correct service, etc.
If it comes to safety and you live in the US you can do whatever you want. Confirm to US law you as the person who is changing safety; take the whole responsibility of the complete safety design of the machine. In case of an accident it is your problem.
I am assuming if you could bypass any safety function just by a little wire, the machine (if the machine is not older 30 years) was never build confirm to US law. US law says since I am working with cutters (and this is about 30 years) that this type of machines (cutters) have to be built by the highest know law. Highest known law would be a safety circuit you can’t just bypass. But I don’t know Challenge and Triumph.
Let’s go back to reality.
How often do you cut the big sheets?
Will this change in the future?
What is a good deal?
What if the cutter breaks down?
Maybe a machine with light barrier is better?
Did you try other sources like the Baum or Polar cutters? I am asking because in the US you have a lot of former Heidelberg engineers, which are providing good service.
Buntpapier