Recreate nodes upon node delete

I think this is a feature request but I am not sure...maybe a bug...

If a user buys 5 nodes to be creating (using pay per node) and they create 4 nodes they should have 1 node remaining. When they delete a node that they posted, I would like their pay per node balance to increment by 1 so that it would show they now have 2 nodes in their balance.

How can this be implemented....if you can point me in the right direction I can try to take a stab at it...