It would be great to be able to adjust the field type after creating the field. 

Examples:

• I create a numeric value ticket field and later I'd like to change this field type to decimal. 
• I create a multi-select ticket field and later I'd like to change this field type to a drop-down. 

The current functionality requires you to deactivate the field and create a new one. However if you've used this field in conditional formatting, you must remove the condition altogether, create the new field, then go back to conditions and re-add the condition for the new field. 

I understand this may not be possible for all field types like drop-down to credit card or multi-select to text but I think allowing the following would be beneficial.

• Drop down to multi-select
• Numeric to Decimal
• Text to Multi-line