While I don't think that Marxism needs a coherent moral philosophy, at least with regard to Aristotle's statements cited by Nussbaum here, there is no need to draw such a conservative conclusion as she does. In fact, one may read these two statements in a way that makes them compatible with Marxism. Marx says:
***** In a higher phase of communist society, after the enslaving subordination of the individual to the division of labour, and therewith also the antithesis between mental and physical labour, has vanished; after labour has become not only a means of life but life's prime want; after the productive forces have also increased with the all-round development of the individual, and all the springs of co-operative wealth flow more abundantly -- only then can the narrow horizon of bourgeois right be crossed in its entirety and society inscribe on its banners: from each according to his ability, to each according to his needs! ("Critique of the Gotha Programme") *****
Marx was no sentimental moralist, nor did he romanticize the working-class life (mental or physical). So one might expect him to agree with Aristotle that universal excellence is indeed impossible under class society, or even under a socialist society while an antithesis of mental and physical labor persists. No abundance of co-operative wealth, no wealth of free time, no universal excellence -- for Marx. Read in this fashion, the above statements by Aristotle support an argument for communism.
Yoshie