Remember the company can cut your job at any time. Unless your skills are so world class that you can get another job overseas quickly, a layoff would make you illegal in that country, without a job, and without a way to move back to the US until you spend the time and money to redo the green card process.
As an executive with an expat contract, it is unlikely and they have to pay you till the end of the contract anyways.
I really want to become a USC but it shouldn't cost me that much money. Who of you wouldn't do the same if given the opportunity?
On another hand, it is really illogic to tax your citizens abroad and to be the only developed country to do so. You give your own citizens (and companies) a competitive disadvantage.