Get what you are saying, but if it were the way you THINK you would like it to be, switching at 7 months would be virtually impossible.
Everyone would buy 50 points at the resort they "want" then stock up on resale points at SSR since they are the cheapest.
It would really F up the system if they allowed what you are asking. (Sorry, no other way to put it, as it would be basically catastrophic if they allowed this)