Without being flippant I have had image softness with 1DsII, 1DII, 10D,G9,G2, Panasonic FX01, Minolta Dynax, Kodak DC210 and Praktica MTL-3. To a greater or lesser extent camera/optical systems have always had some form of limitation whether it is resolving power, aberrations or distortion.
In the case of the 1DsIII it is a case of what are you trying to trade off (cost, weight, resolving power, contrast, tint, bokeh, aberrations, distortion, vignetting, etc...) and selecting the lens accordingly. There will be no perfect solution and you are going to have to accept some form of compromise.
The 1DsIII will show every limitation of the lens and you will need to decide what you are looking for and which lens works best for you - you will need to be more specific on your requirements and which compromises you are prepared to make.