The issue with laying off senior management is that if, for example, your head of HR leaves, then you still need someone to run HR. Maybe if they promote someone into the position it will be cheaper, but not necessarily by a huge amount.
I know countries where that would be illegal. It is the role that is redundant , is no longer required and cannot be refilled within a certain timeframe. You cannot make a position redundant and then promote someone to that position. If needing it refilled, then it wasnt redundant