My ideal tool would let me switch a knob to turn on io profiling and then would let me drill down into the trace, show what processes caused the io, was the io like (contiguous vs seek heavy, fsyncs, etc). A second need is report what kind of io a process incurred during its runtime, a bit like "time".
I guess much like "perf" now but for io.
For all I know all the kernel pieces are there already. We do have some newer tools like iotop/iostat that are small steps forward. But it's pretty quiet.