Goals can't be created in performance document in redwood

Goals creation and updating is no longer supported in performance document in redwood. Since our customer is using setting goals option in process flow, we have created new process low, new performance templates, new template sections with synchronized goals section checked box checked.
We are planning to go-live in production for redwood in the month of July.
Since our customer review period starts on 1 Jan of the year and ends on 31st dec every year. their performance documents are in middle of the evaluation process, employees and managers already started creating respective goals.
So, when we enable redwood, we will be cancelling old performance documents and creating new performance documents in redwood for all employees, so customer is going to lose data, goals created in old performance document.