Often when a base starts off, look-up fields are appropriate for several use cases. As the scope increases, roll-up fields looking at the same fields become much more valuable. However, changing to a roll up field is not a simply click or two.
A Use Case
Currently when changing the field type of a look up field to a roll up field, the properties of the look up field are erased and both the linked record field and field to be looked up must be input again. This requires several extra steps to make sure I remember the setup correctly (especially with several similar or progressive fields in both tables). Typically I create a copy of the look up field then use it to double check my roll up conversion.
My most common conversion is to introduce an ARRAYUNIQUE(VALUES) function when we begin to see duplicate information.
It would be incredibly helpful for the settings of a look up field to be preserved when the field type is changed to a roll up field.