This sounds like it might require major, major overhaul of the points system, in order to track what points came from where. It seems now to be a straightforward system where something acts to change your points total, and then you have a new total number in your pool of points. Difficulty to implement is of course not a complete this-will-never-happen, but ... it's a blogging site, not a banking system.

Also, not to sound callous about the disposition of money spent by users, but points that remain unused (like points that are in the possession of a user when they delete and thereafter become purged) are to the financial benefit of the company (though users deleting themselves are not to the company's benefit). Though I imagine that the owners are not looking to have this happen, because of how having active and not deleted users is a good thing.