Minor suggestion Nicolas:
Currently, oc-natbib ignores global affixes.
This makes some sense given natbib has no notion of global vs per-cite affixes.
But it seems ideally the code would preprend the global prefix to the local prefix of the first cite.
So [cite:global ;local @doe] should yield \citep[global local ][]{doe}.
Not sure about suffixes; maybe (?) those are best ignored.
Bruce