Reloading Demand History for Few customers in Fusion Demand mgmt

Summary:

In Demand Mgmt cloud, Business wants to reclassify certain Customer groups and want to reload demand history in Fusion by deleting the old history 

and reload new ones for those specific customers back to Fusion. Our Forecasts are primarily based on bookings history data but we 

also load shipment and measures in the system as well.

Do we need to load any measures as well along with bookings and shipments history?

Also, is there a way to delete bookings/shipment data for specific customer groups in fusion or can it only be done through FBDI using delete_flag? 

I know we have purge functionality but that only works with dates and not customer or customer group specific.