So, if you were really pissed...
Ask if the dealership accepts credit cards, which they do I am sure. Get a money line with your house which will have a low rate. Negotiate, then when you don't get what you want, tell the guy you will pay now. Pay with the credit card, and let them eat the credit card commish.
My father in law did this to some a-hole sales manager when they tried to change the deal, just as you describe. Needless to say, the manager instantly caved.
In all seriousness, take the independent lease deal.