As I already wrote, that is basically what folders do now. They are forced to be treated as transactions with no line items. (See my post #12.) Customers/suppliers might also be forced to be treated that way, but you would not see important information like code, currency, delivery address, email address, credit limit, and active/inacactive status. While the program uses those fields for other purposes, they do not show in a theme-controlled View (except for delivery address in place of billing address on a delivery note).
And while custom fields can be made to show in a theme, they are not used by the program for essential functions the way the other information on a customer/supplier Edit screen is. There is no point is requiring double entries of information. This still comes down to controlling what a restricted user can do: view and edit versus view but not edit.
Please do not misunderstand me. I am not arguing against finer control of user permissions. I just think that is a more useful way to approach this issue than to incorporate View options for customer/supplier information that are not very useful.