A few points:
1: The prenup descibed has no incentive for the woman to comply. I would believe it more if the woman would also have a similar K’nas.
2: Making a kinyan to pay is difficult at best. I would imagine that another bais din would find it unenforcable.
3: I agree here 100% with Tomche (I’m shocked too) that it should only cover reasons that Halacha considers to be acceptable for divorce.