Doesn't have to be rules, just a guide and companies who comply and those who don't.
For an example how this could work, see the CFA and GIPS. Every big asset manager is in compliance with GIPS. Every reputable startup should choose whether to be compliant with best practices for equity for employees.
That word has already gotten around and is one of the main reasons for ageism in the industry - the only people who will work for startups are those who haven’t been burnt or wised up yet.
This is an interesting thing to consider. If you look at the current president of YC (sama), at least from an outsider's perspective, he's the beneficiary of exactly the type of behavior you're trying to get away from. Based on his company's exit, he is now a VC, but his company was acquired for essentially what it raised, meaning the employees' stock was likely worthless. I have absolutely nothing personal against sama, but let's remember that YC doesn't exist as a charity, it's a business.
I cant imagine one measure increasing salaries and efficiency more than allowing employees to trade stock.
But let's also remember that the people running YC are adults, fully capable of telling right from wrong, and fully capable of being held responsible for their actions. Being "a business" is no more of an excuse for their actions than "following orders" is.