Many firms give the dealer an ERP username. The dealer then sees your accounting language, not their own job. Orders land on the wrong account, internal modules are visible, and support calls rise.
A portal’s job is narrow: this dealer’s price, balance, open orders and shipments. Internal cost, another dealer’s record and the staff menu are not there. Permission is a boundary on data, not a role name.
A good portal does not replace the ERP. The ERP stays the source. The portal reads what the dealer is allowed to see and writes the order back. Accounting keeps the screen it knows. The dealer places the order without calling you.
Three questions are enough before you build it. What does the dealer call you to ask? What must they never see? Who approves the order inside? Those answers are a better brief than a list of screens.