right now, the possibility of lost coins leads to the risk of an incalculable profit for everybody owning bitcoins. the possibility of recycled coins on the other hand leads to the risk of an incalculable profit for everybody mining bitcoins.
so you basically want to put an awful lot of work into it and make the protocol more complex just for trading one problem that isnt really a problem for another not-really-a-problem.
thats so meaningless you could probably convince the european union to fund it