That's great at and all, but I honestly don't understand how that would help in this situation. Unless you write something absurd like "Mark Zuckerberg's stock will be transferred to Palmer Luckey if this promise is broken", which just about no one in Mark's position would agree to, how are you going to actually prevent something like this from happening?

edit: and as ComputerGuru stated - such a clause can just as easily be put into a traditional contract