Does anyone here have an idea how to sharpen a blade like http://images.knifecenter.com/knifecenter/coldsteel/images/CS62KGM.jpg for example?
The stone would be too wide and a portion of the blade would remain dull.
That is precisely why I do not buy knives like that. Even the less sweeping blade of a kukri is difficult to do.
So I won't be able to sharpen this knife?
You can take the coarse side of the stone grader and create a radius on the corner of the grindstone, then carefully use the radius to work the inside curves. It's doable, but takes practice. Get very comfortable with freehand sharpening before going after this one.
Recurves are very hard to do on the tormek i would suggest going freehand.
Buy some different sized wooden dowel and some automotive wet and dry paper up to around 1200g. The radius of the dowel should conform to the curve of the blade, and with abrasive paper glued around it can be used to sharpen the edge. Work through the sand paper grits until you have it sharp, then add some of the tormek paste to a clean piece of dowel and use to polish the edge.
Use magic marker to help you match the angle and go slow. If you are worried about scratching the face of the blade, wrapping all but the edge in decorators tape can save a lot of annoyance