Hi Tushar,
I have few suggestions. Hope one of them works
1. In the first page of Customer Details section there is a Business partner Id grouping. For me if i select the drop down values then that same value should be selected in the new ERP Customer page as you have shown and on successfully submitting the CR the Customer # gets generated.
2. You can set the role to default like FLCU01 for customer. If you can do that successfully then you can see the dropdown enabled in New ERP customer section. This default of role can be done via handler class enhancement.
3. Lastly go to MDGIMG>ProcessModelling>ChangeRequests>Edit Status of Change Request.
There for each of the statuses as per your requirement you can select the value Execution of Changes to make all fields editable.
Try the 3rd option first.
Thanks,
Subhronath