Something I've wanted for a long time, and maybe I should drop the idea now.
There's a lot of Python objects that are really little more than wrappers around an opaque C pointer (plus all the methods to operate on it, etc). These objects usually have accompanying Parse() and Build() functions, that you pass to the O& format for PyArg_Parse and Py_BuildValue.
This all works fine, but I think we can do one better. If we have slots in the type structure to store the Parse and Build functions we could add a new format specifier O@ (or whatever other character is free:-) that has a typeobject parameter and a C pointer parameter. One advantage is that this would fit a lot better with the new class inheritance scheme. Moreover, and more importantly, this would give us a handle to use from Python code, so structmodule could (un)pack structures that contain pointers to objects that are python-wrappable, calldll could neatly wrap functions that have python-wrappable objects, etc.