How to customize "Supplier Type" field in "Request New Supplier" to default value

Summary:

We have a requirement to customize the Request New Supplier page in Self Service Procurement.

The Supplier type field should be read only and it should default to a specific value from the POZ_VENDOR_TYPE lookup.

All users having the SSP access should be able to request new supplier using only this specific supplier type. Certain users who have supplier admin roles will be able to select any other value in this supplier type field.

New Supplier requests from the end users will be approved by users having the Supplier admin role.

Content (please ensure you mask any confidential information):