Allow custom form field formats to be changed without losing historical data

Description - Our custom form fields were created 11 years ago and over the years things have changed and several field formats need to be changed, however, as of right now, there is not an easy way to change the format of a custom form fields without losing historical data (ex: changing a field from a drop down to a free text field)

Why is this feature important to you - allows users to adapt new workflows or changes in workflows without losing historical data

How would you like the feature to work - Allow field format to be changed without losing historical data

Current Behaviour - currently a form field format cannot be changed once it is created.