Sale & Issue of Stock Items

Hi

We sell various hardware items.  Suppose we are selling Item A.

Item A may be issued from Stock in 3 ways:

1. at the standard price, paid in full by the customer on invoice
2. on a hire purchase (rental to purchase model), paid over a term of 36 months
3. free of charge as a warranty replacement 

In each case the Item is identical so I don’t want to create more than one Inventory ID.  As far as I see Subitems or Attributes would require me to do so.

Currently we distinguish between these models as follows:

1. price applied is the list price
2. price applied is the list price with 100% discount
3. free item box is ticked

Is there a better way to identify these different commercial methods on a Sales Order, such that we can report on them conveniently later?