Can 1099 salaried employed be changed 1099 hourly employees?

People who are paid by 1099 are not employees to start with, they are contract workers, you may contract them to work for specific amounts for certain jobs, or contract them to work by the hour,

When paid they have to ( or should be) paid enough that so that they have to pay their own taxes, including self employment taxes.

Also you need to stop using the term employed or employees, they are contracted, not hired