Totally agree that usually, the more upfront cash you get, the smaller piece of revenue you get. However...at least in entertainment, sometimes we use what is called a "corridor", whereby until that upfront amount plus a vig is paid off, the investors gets X percent and then after it's paid, gets a smaller percentage on an ongoing basis.
For example, CYDY gets a $100mm upfront payment with terms being 80/20 (partner/CYDY) until $120mm is paid off and then it becomes 60/40.
I wonder if that is ever used in biotech. I honestly have no idea, but it's at least something to consider in negotiations.