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