I am not trying to argue, full frame is the way to go as long as you supplement it with good lenses. I read this article while a go about full frame vs APS-C and effect of different lenses. They done extensive test showing the importance of very good lenses for full frame especially wide open. Anyway these differences do not really matters unless you are going to make very large prints.
There a couple things you mentioned that are not correct (or I misunderstood you). Image circle is pure property of lens and has nothing to do with sensor or film. Image circle in very crucial in large format photography for perspective control or to increase the DOF. You need large enough image circle to cover the film while you are shifting or tilting front or rare plain. The image circle is also bigger than normal in PC (perspective control) lenses offered by Nikon and Canon to allow you to tilt and shift the lens to correct the perspective.
Again, maybe I misunderstood you with regard to composing ability. Asus jan, if you consider the film size (or the sensor size) to be a canvas or drawing board then the size of your created image (or composition) will depend on the boundary of your canvas. So if you are using large format (8X10 or 4X5), medium format (6X9, 6X7, 6X6, or 6X4.5), or SLR (full frame or APS-C) you have a fixed area to compose your image. So by moving from large format to small format as you mentioned your composing ability does not change but in fact your canvas size changes (and I am not talking about crop factor). 50mm lens is normal lens on full frame SLR, while 80 mm lens is normal for medium format and 150 mm is normal lens for 4X5 format. As you move up the camera format the image circle of lens increases to cover the film size. The image ratio falls between 1.2-1.5 in different format camera (except in 6X6).
Since you are going to buy 5D MII and 24-70, maybe you should mail order it from another Provence, you will save big time on PST. I am planning to buy Nikon 14-24mm F2.8 form L.L. Lozeau (mail order) or B&H to ship to Ontario.