"If the subjects of the conjuncts are the same and the substituends of N are univocal across the conjunction, then as long as the reduplication predicates being A of x and predicates being B of x, and being N is entailed by being A, and not being N is entailed by being B, then the reduplicative form of predication accomplishes nothing except for muddying the waters, since in the end the contradiction stands of x being characterized as both N and not N."
In other words, if the subject (x) is the same, and the property (N) is the same then 'x as A is N and x as B is not-N', when A implies N and B implies not-N, just is to say 'x is N and not-N'.
The problem with this objection is that it is simply wrong. I hold for an explanatory account of reduplication, in which the reduplicative phrase explains how or why the predicate applies to the subject. This means that while the term N might have the same meaning on both sides of the conjunction (and thus be univocal in that sense), it does not follow that the predicate 'is N' is predicated univocally. To put it in other words, using the same term with the same meaning doesn't entail using it in the same way. Reduplicative phrases mark difference in predication. There are many other sorts of phrases besides reduplicative ones that do the same sort of thing. For instance, I can say "Tom is strong when healthy and not strong when sick". This does not imply a contradiction because 'when healthy' and 'when sick' explain the application of 'is strong' (or 'is not strong') to the predicates in such a way that they apply to the subject in different respects. The predicate 'is strong' applies to Tom when he is healthy; the predicate 'is not strong' applies to Tom when he is sick. There is no contradiction.
As I said, there many similar sorts of instances. Reduplication is an example of this: reduplicative phrases explain the way in which the predicates apply to the subjects. Thus, when we say, "Christ is omnipotent as God and not omnipotent as man," we are tracing two different explanatory paths, saying (in effect): Christ is omnipotent in a sense and not omnipotent in another sense. The only way you can pull a contradiction out of this statement is by arguing that it is contradictory for a single subject to be both God and man: in other words, the different explanatory paths block contradiction unless the explanatory paths are themselves in contradiction. It is impossible to draw a contradiction from "Christ is omnipotent as God and not omnipotent as man" unless there is a contradiction in "Christ is God and man".
There is also the further point that being man does not entail not being omnipotent; being only a man, or being human and nothing else, does. If a human being can only be human, and not something else as well, then there would be a problem for the reduplicative approach - but again, only because such a claim would be tantamount to saying "Christ is God and man" entails a contradiction.