Terrible idea imo, there is almost no company that can't cut 5% of their staff without negatively impacting the company as a whole if done more or less right, you cut the people who are lower performers - or average performers who, thru no fault of their own, are not currently assigned to something that matters anymore to the company.

Cutting the pay of the best/better performers, and/or the pay of people that are actively contributing to high value projects, so the less qualified or less needed people can stay employed seems like a huge disincentive to keeping your top performers.

If my manager came to me with that proposal I would give my notice on the spot.