A first thing would be to select a suitable prefix name for the Array
API. Because the Numpy people have 'stolen' PyArray_ instead of staying
home with PyNDArray_ or so ;-)

In case sb goes into this:
Other than PyList_ like stuff and existing members, think for speedy
access (like in Cython array.pxd) a direct resizing, the buffer pointer,
and something handy like this should be directly exposed:

int 
PyArr_ExtendFromBuffer(PyObject *arr, void* stuff, Py_ssize_t items)