Help needed in changing existing hierarchy

Hello All,

Need  your advice for below requirement:

Requirement: Customer wants to change the parent hierarchy of Item in Demantra as below (Item is lowest Level and Product Line is highest level, parent of Item)

Old Product Line	Item	New Product Line	Item
PL1	IT1	PL4	IT1
PL1	IT2	PL5	IT2
PL1	IT3	PL6	IT3

All data (Forecast, history, lag)associated with Old Product Line should move to new Product Line.

We have 3 years of data in Demantra now.

Thinking of apply any of below 2 solution, but not sure is there any risk involved.

                Solution 1: Export all data for the product lines one at a time and import it with new product line information. Before importing void/disable the existing product line. (Looks like this would be time consuming since you have huge data and not sure can we miss anything)