Allow upload of new CSV to existing dropdown field

Feature Request Summary: 

Allow existing values to be deleted and a new CSV to be uploaded on an existing dropdown field.

Description/Use Cases: 

We have many fields that include locations, job profiles, and more which are routinely updated. These dropdown contain hundreds of values. Also, a good chunk of our help center jQuery is predicated on certain field IDs. Replacing existing dropdown instead of creating a new field would:

• Preserve existing conditions on ticket form
• Save field IDs in custom code (no new fields to create)
• Preserve existing ticket metadata
• Preserve existing data on ticket form (since these forms are used almost daily, deleting and replacing a field means more work on agents to go back and re-fill the information)
• Preserve existing ticket field tag data, since we won't have to deactivate, delete older ticket fields or create entirely new tags (which disrupts scripts, conditions, triggers, etc).

Of course, one could do this one-by-one - but again, with hundreds of values, that would be an incredible time sink.

Business impact of limitation or missing feature:

The process of replacing whole dropdown fields with entirely new fields is time consuming for admins, and wastes agent time when re-filling fields out on existing tickets. Currently, to update jQuery, conditions, forms, etc. it can take upwards of 20-30 minutes per field. 

This could theoretically be accomplished via API. Not everyone is privy to script writing, and this feature would be an incredible one to have natively within the interface.