Supplier portal personalization

Summary:

What is the best / recommended way to do personalization in supplier portal screens .
For example we want to do a personalization in supplier portal's invoice creation screen to make some fields read only.

We understand that to access supplier portal one should be defined as a supplier contact and
user account should be created for the supplier user. In order to do personalization
by creating sandbox the supplier user should be assigned "Application Implementation Consultant" role ?

Is there any other way to do personalizations in supplier portal screens without assigning

the powerful "Application Implementation Consultant" role to supplier user?