Can an absence accrual plan be updated from incremental to frontloaded?

Summary:

Our existing absence accrual plan has been set up as incremental for accrual, but the policy might allow it to become frontloaded in 2025. Can we update the existing plan or create a brand-new one?

Content (please ensure you mask any confidential information):

Currently, thousands of employees are enrolled in the above plan, which has existed for two years (some active enrollments started at the end of 2022). If we end date the enrollment for all employees as of 12/31/2024, can we update the plan to be frontloaded as of 1/1/2025?

Our plan is based on a monthly accrual, with some balances frontloaded as of Jan 1 each year.