I'm not sure what you mean by "paying an equity grant". If you fire someone they no longer receive new equity. And for a company that's been public for 4 years with a constantly dropping stock price I doubt the volume of early employees exercising options could possibly bankrupt the company. I don't understand how that could happen to any reasonably well managed company.

>Even among its Silicon Valley peers, which have drawn closer scrutiny from investors recently because of their generous stock-based compensation practices, Twitter is notable for how much equity it doles out.

>And those grants of restricted stock units or options, which would have to be covered to some degree by any buyer, simply add to the purchase price of any deal.

>According to Twitter’s most recent annual filing, the company racked up $682 million in stock-based compensation last year. By comparison, the company’s adjusted earnings before interest, taxes, depreciation and amortization — which also excludes stock-based compensation — for the year was $557.8 million.

>Factoring in the payouts would have pushed Twitter well into the red for the year.

https://www.nytimes.com/2016/09/27/business/dealbook/twitter...

Is a grant an option? No. A grant is a grant. The employee isn't buying the stock at some price. The employee is being paid in equity with a grant. It's stock that's been issued in lieu of higher salaries. And yes, if an employee gets a grant vested you must fulfill the grant even if the employee leaves after vesting. You can't just hire people and refuse to pay their compensation.