I would totally do this trade. Jacksonville looks horrible and I don't see that changing anytime soon. Mendenhall is a stud right now and should remain so even when Big Ben returns. Desean Jackson is really clicking with Vick's cannon arm at QB so I see him as a huge upgrade over Moss/MSW.
QB - A Rodgers, E Manning
RB - A Foster, S Jackson, R Mendenhall, T Jones, R Bush
WR - G Jennings, L Fitz, S Smith (Car), P Harvin, V Jackson
TE - A Hernandez, J Tamme