"In any negotiation, you have to be prepared to walk away if you don't get what you want.
I'm self employed and have walked away from customers where their terms didn't match what I was prepared to accept. The point was, I had to be prepared to walk or the threat would have been pointless."
Could you explain how this is a sound business idea if:
a) your potential customer is just as happy to go to a rival firm instead
b) the rival firm has more clout and more resources than you
c) your customer have more to lose by rescinding trading deals that affect the whole of the rest of their business than they have from losing the trade with you
d) the credit of their whole business depends on not being seen doing underhand deals with you
e) it is unlikely that you would get any new workable contracts within the time you need to keep your business afloat.
???