Unfortunately I don’t have time to flesh out anything particularly worthwhile about it right now, but I came across an interesting review of the very promising Franz Rosenzweig and the Systematic Task of Philosophy:
Kant was the thinker who placed the idea of system on philosophy’s agenda, although Rosenzweig thought it had always lain like an embryo waiting in the womb of philosophical rumination. Hegel and Schelling seized on this in particular, and formulated their systems as responses to the new challenge. A century later, however, the landscape of philosophical questioning had substantially changed: how to view the question of system seemed in a precarious situation that is ultimately unsatisfactory.
Continuing:
Is the ‘system’ still an option for thinking the Whole or, to put it in Hegel’s famous phrasing, to grasp one’s own time in thought? In philosophy, the form of system has pretty much faded from general debate since the flowering of neo-Kantianism in the first third of the 20th century. Among the tendencies running counter to such attempts are the huge material and methodological differentiation of the various sciences, the obligation sensed everywhere in the West to remain ‘open’ and receptive to other cultures, and the numerous efforts to construct a hermeneutics of historical-biographical phenomena, extending all the way to a philosophy of everyday life.
Over against this decline in system thinking in philosophy there looms a veritable boom in building systems in other spheres. Today we seem to encounter concepts of system wherever the description and theory of certain sub-spheres of the world, life or human existence are concerned: in cosmology, ecology, economy, biology, sociology or psychology. However, the systems theories in biology, sociology or the information sciences, for example, do not regard themselves as direct descendants of those older efforts in philosophy to contemplate the “unity of the One and All” in the framework of a system. The anarchic element inherent in these tendencies, and more generally the consciousness of the fragmentary nature of everything that can be done and achieved, would appear, at least in the realm of philosophy, to be in direct opposition to the form of thought of a grand system. If nonetheless one wishes to preserve rather than jettison the question of the Whole and the ‘universe’, the “All”, as a motif in philosophical questioning, then despite those objections, the figure of a system must be critically examined anew, perhaps in a way still seldom applied. That is the basic question with which Pollock confronts and interrogates Rosenzweig’s work.
Rosenzweig formulated a system that does not deny those anarchic elements. On the contrary, it draws its sustenance from them. With his system, Rosenzweig wishes to lead us on to the threshold of everyday thought in its concrete simplicity. But more than just discursive thought is important here. The concrete experience of what is thought plays its decisive role in life with the same weight (cf. Pollock, pp. 235-257). Thus, as Pollock convincingly describes it, Rosenzweig’s “system of philosophy” also assumes a figure, and can be experienced in all its stages in that Denkfigur. In its graphic character as ‘figure of thought’, the “star of redemption” becomes a motor for construction of a system, from the building blocks of its structure down to its finished final form.
Interesting. The reviewer, Hartwig Wiedbach, concludes:
Precisely when it comes to encyclopaedic or medical systematicity, Pollock’s central thesis that a “system of philosophy” in Rosenzweig’s sense must not only be thought but also experienced is intriguing. Whether that is possible is decided not only by the coherence of an author of a system in terms of its exposition and conceptions. Its possibility is also determined by the success or failure of an attitude toward the realities of everyday life and death acquired through experience along its way.
Perverse Egalitarianism 
These are interesting observations about systematicity. Is the book already out? Is there a connection between, say, thinking systematicity and thinking systematically (what sort of thinking would that be?) – Kant’s system was left unfinished (if we are to believe, say, Eckart Foerster) – but does it really matter?
Yes, the book is out. I just ordered it through ILL.
As for Rosenzweig’s relation to “systematic,” “systemic,” “systems,” “holism” or why not, “networks” etc. I think it is best understood against the background of many of the philosophical debates from the early 19th century in response to Spinoza’s ontology of relations, really. Paul Franks touches on this in an article/rejoinder to Peter Gordon’s book on Rosenzweig and Heidegger in the Jewish Quarterly Review from 2006 (I can email you the article if you want):
I’d like to see it, yes, can you email it to me?
This is the same Paul Franks that wrote All or Nothing, the book Alexei recommended a while back and the book I really liked, by the way.