A nonrefundable ticket can be used to pay for a refundable ticket. It's just that the ticket won't be refundable! Those funds can not be refunded, and all restrictions (change fees) applicable are to the lowest common denominator. So, no, your scam won't work.

For example, say you book in advance a $300 fully restricted ticket. The day before departure you have to change flights and rebook; the new fare is $1000, fully refundable and unrestricted. You will have to pay $800 (your original ticket value is now $200 because of the change fee). That $800 is refundable. The initial $200 from the first ticket is not. The new ticket is as restricted as the first, so any changes will result in a change fee.

This is how I understand it. Thus, in the scenario described above, I always in the past just bought a new ticket that had no restrictions and used the value of the first ticket for future travel on restricted fares.

THIS QUESTION IS IMPORTANT AND HAS YET TO BE SUFFICIENTLY ANSWERED: Under the new policy, if I call to cancel a nonrefundable ticket before departure, must I immediately book a new flight with that ticket? Or can I just get credit valid for one year (From inital purchase) for future travel?

Thanks.