He doesn't want 'two kinds of bishops'. That's exactly what the Code of Practice will give the C of E: those bishops who because of their gender have to negotiate their way with the awkward squad; and those who don't.
With a 'diocesan' solution, the bigots would have been coralled into their own dioceses and the 'mainstream' dioceses would have been entirely discrimination-free: no resolutions, no codes, no petitions, no shifty archdeacons with their illegal nods and their winks ('Trust me and I'll see you don't get a woman vicar').
I can only suppose that the Establishment are gambling on a policy of holding their nerve and seeing us disappearing or being crushed into grudging and sulky submission before the question becomes a practical one. It's a dodgy gamble because if they lose it the women bishops will curse the poisoned chalice the 2008 Synod mixed for them.