Option to link or share custom fields between Features and Ideas, so choices only have to be managed once Merged

In APP-I-1989, there is a suggested workaround to promoting categories from Ideas to Features, which is to use Custom Fields instead (which in itself seems a bit odd). Anyway, I have gone along with the advice and have set up matching custom fields in my Ideas and Features, using the Field Type of Tags field. However, whenever I add a new option to either custom field, I have to remember to add the same option to the other custom field.

It would be great if one of the following enhancements could be made:

1. Give some consideration to being able to promote Categories from Ideas to Features
2. Manage one Custom field and choose of you want to use it in Features, Ideas and Master Features
3. Create a link between matching Custom Fields (in Ideas, Features and Master Features) so that, when an option is added to either custom field, it is automatically added to the other

This might only be an issue for Custom Field Types of Tags fields or Choice lists, but it's still worthy of consideration when creating custom fields of these types.