RodW, I guess you missed the F2 key, that brings up the customer and allows editing, in all the documents.
By changing the row 45 in /sales/inquiry/customer_inquiry.php to:
customer_list_cells(_("Select a customer: "), 'customer_id', null, true, false, false, true);
will enable the F2 key so you can look at the customer. This will be changed into the HG repository.
The theme, exclusive, has a lot of the features you request.
At first, let us just stay with the links between the forms.
/Joe