Recreating the field as described in the KB article will be needed. To save the data tough export the data stored in the field that have to be changed or save the data in another field trough the API.
DynamicModuleManager dynamicModuleManager = DynamicModuleManager.GetManager();
Type iedcnewsType = TypeResolutionService.ResolveType(
var liveItems = dynamicModuleManager.GetDataItems(iedcnewsType);
var fieldToBeDeletedValue = item.GetValue(
//export to suitable format
//copy this field data in another field, or a field created just for this purpose
Also instead of exporting the data create new module with the module builder and create items for this module that will hold the field values (those items can have the same titles as the items in your module for easier import back to the original module).
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