I know the ship has sailed on this conversation, and there are plenty of more comprehensive and enlightening blog conversations out there from the days following the article's actual publication. This short bit from Milbank struck me when I first read it, though:
"[...]without the addition of power to charity would the church have survived at all? To refuse this addition is in a way to refuse the resurrection, and the fact that in the end it is Christ's kingly role which is eternal, and not his mediating priestly role."Who says Milbank's work isn't properly christological or focused upon the resurrection?! Actually, I wondered whether this made its way into his explanation partially to counter such characterizations of his work. He cites no source here, but the logic reminded me of the Norman Anonymous, which I considered in my recent article (564-565):
It is also worth noting how the Norman Anonymous distinguishes the extent of the kingly reign as opposed to the priestly. In the last quoted passage, the Anonymous states of Christ, 'regnabit in eternum et ultra. Qui sacerdos dicitur in eternum, non ultra. Neque enim in eterno vel ultra eternum sacerdotium erit necessarium.' The royal role, therefore, goes into eternity while the priestly role extends to eternity, but no further. This ironically grants a greater dignity to kingship even though it is based on the scriptural claim that 'you are a priest forever'. It is also notably in contrast to other contemporary exegetical traditions that are not so much 'papalist' or anti-royalist as they are simply anti-hierocratic. Philippe Buc has described what he calls 'pro-egalitarian' exegetes who rejected the hierarchical conception advocated by Isidore of Seville whereby the domination of humanity over creation was allegorized into an explanation of temporal rule. In contrast to the kingship existing into eternity that the Norman Anonymous presented,
their early Gloss on the Pauline Epistles incorporated a startling denial of the permanence beyond the end of history of any form of hierarchical authority. On 1 Corinthians 15:24, 'When He will abolish every principality, every power and every virtue,' the masters commented: 'As long as the world lasts, angels govern angels, demons govern demons, and human beings, human beings, to serve or deceive the living. But when all shall have been gathered, then all power (prelatio) shall cease, for it will no longer be necessary.'
 Williams, The Norman Anonymous of 1100 A.D., pp. 128-9, Libelli de Lite, Vol.3, p. 663.
 P. Buc, 'Principes gentium dominantur eorum: Princely Power between Legitimacy and Illegitimacy in Twelfth-Century Exegesis', in Cultures of Power: Lordship, Status, and Process in Twelfth-Century Europe, ed. T.N. Bisson (Philadelphia, 1995), pp. 310-28, p. 316.
The argument isn't exactly the same: Milbank (sounding very Protestant, ironically) wants to mark a discrete end in Christ's priestly work with His death, whereas the Anonymous sees Christ the priest as continuing to eternity. But the idea in both cases is that one way or another, kingship goes beyond priesthood as a christological office, and so it should be privileged in political thought as well.
Milbank is often identified as "medieval" in his thought. Sometimes this is proclaimed as a good thing, and sometimes it's meant to be derogatory. In either case, though, it always seems like an incredibly vague identification. Here, perhaps, is a suggestive possibility for whom Milbank might actually have in mind when he follows certain lines of argument. The connection is further recommended by the prominent place of the Anonymous in later Anglican thought of an Erastian bent. More importantly, the quote from Buc brings to the fore other exegetical possibilities from a historical period that is usually just assumed to be cornered by certain of today's nostalgic modes.