The fact of the matter is that any member of staff can leave whenever they wish to, and can not be held to working a notice period. They would lose any monies owing to them by the company in lieu of notice.
Most responsible people will work their notice period - 1 week, 1 month or 3 months depending on seniority.
Anyone leaving voluntarily will lose any redundancy pay that they may have been entitled to, had they remained employed and been offered redundancy or made redundant.
As a consequence of all that, the only people who should leave are those with another good job to go to. Everyone else should, in their own interests, stay on.