Self-service interface to guide users for "Enter Requisition Line" similar to smart form

Summary

Is it possible to create forms (like smart forms) to guide the users, but to add an item on the form?

Content

Hello everyone,

My client has different types of requisitions that require different fields to be filled when requisition lines are added manually. For example, for requisition lines over 10 000$, they need a negotiation, and therefore need the field "negotiation required" to be checked. We are working on finding a way to guide the users on choosing the right parameters for the different types of requisition. 

The feature that nearly perfectly fit this requirement was the smart forms. Therefore, the users could choose the smart form according to the type of requisition they need, and the fields they need to fill would be clearly indicated, which would reduce the risk that they make mistakes. However, smart forms don't allow the user to enter an item, which is essential.