What a horrid idea.
We have been told that if you are sick with possible contagious symptoms to not come in. You don't have to take PTO if you are coughing a lot but they don't want you in the office.
Or, shocking I know, there are people that work in the office all day AND then work some more at home in the evening. Or on weekends.
Those are just two of many reasons why your idea is just awful.
The problem with RTO attendance will solve itself. If you aren't compliant you will face consequences, including being put on performance improvement plans. Managers are now being held accountable for their employees. If they don't take action as managers, their managers will take action against them. People will be forced out of the company or forced into RTO compliance.