GNU Radio, One Step at a Time: [Discuss-gnuradio] about the work function and memory

Here is a typical work function:
int work(int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)

output_items seems to be a pointer to a pointer into some pre-allocated
memory. What is stopping me from managing my own memory, pointing the
output items pointer into my memory, and returning an arbitrary
noutput_items?

Is it possible? What are the limitations?