The Requisition Worksheet
The Requisition Worksheet has interactions with the Purchase functionality of Dynamics NAV, since purchase orders can be created as the result of running the Requisition Worksheet.
However, it also has interactions with items (as they hold the replenishment parameters that the Requisition Worksheet will use), (since the Requisition Worksheet will check this functionality to get the demand of items), and with other functionalities that represent the demand of items (item transfers between locations, production components, service orders, and so on), and again with the Purchase functionality (since the Requisition Worksheet will check this functionality to get the supply of items) and other functionalities that represent the supply of items (item transfers between locations, inventory, production, and so on).
The answer to the question of how those functionalities will have to change, in the case of using the Requisition Worksheet, is that they do not have to...