How Do I Create Custom Transaction Form RO Except for Custom Fields?

How do I create a custom Transaction Form (Sales Order) for a specific Role which does the following:
[LIST=1]
[*]All Built-in fields are Read Only (RO)
[*]Hide the Items tab, or at least make another custom tab be first
[*]Only the fields on this custom tab can be edited by this role
[*]The record must be saved with the same form it was created with[/LIST]Here is our use case:
[LIST=1]
[*]Sales Order is created by Order Dept using Custom Form "SO Entry"[LIST]
[*]An onsubmit script populates a custom Route tab with custom fields[/LIST]
[*]Later, the Transportation Dept needs to edit the Sales Order for the sole purpose of changing some of the custom fields on the SO Route tab