Orders vs Invoices and order number vs invoice num

I understand the 'legalities' of other countries related to orders and invoices; however, here in the US having different order numbers and invoice numbers is confusing end users.

I need to have one number used on all forms.

I was able to just disable the invoices from being generated (so all users see is their 'order') however, that leaves me without some functionality.

Is there any way to go back to having just one number that is used for both orders and invoices?
(Even if I need to modify the output layouts to just display the 'order number' on the invoice.)

What are others using in the US that want a single 'number' throughout the process?

OK ... now it makes sense.
However, if I don't make a change there, then everything stays displaying as 'order'.

It would be nice to have the ability to make that change (i.e. setting when an order becomes an invoice) but yet having the same number used.

Probably easiest way would be to just add a new 'option' i the "Invoice Number format' field for something like {ordid size="5"} that would allow us to pull in the numbering sequence from the number generated for the order number (although without the 'format' of the order.

So that we could enter:

ORD-{date format="m-d-Y"}-{id size="5"}

INV-{date format="m-d-Y"}-{ordid size="5"}