I'd also look strongly at the new Sony RX10 (not to be confused with the RX100). It's quite similar to the FZ200, but has the much better performing 1" sensor, same as the RX100mkII. The telephoto lens only goes to 200mm equivalent, but with 20 higher-quality megapixels, the images should be more croppable than those from the FZ200.
The others have made good points regarding compromises. You can't have it all. FZ200 compromises image quality for size/weight. By comparison, the RX10 compromises a bit of telephoto reach for image quality.
I would have thought that u4/3 with the Panasonic 100-300 would have been the ideal solution for you. Reasonably light, quite good image quality, and reach up to 600mm equivalent. Are you sure that u4/3 is too large?
Another possibility would be a Nikon 1 (preferably the V2) with FT-1 adapter and Nikon 55-300 or 70-300 DSLR lens, which would give you an 800mm equivalent, with DSLR-speed continuous AF, and 14MP of 1" sensor goodness. Probably wouldn't be smaller than the u4/3 solution, but would have better AF and more reach. Plus the ancillary non-telephoto lenses would be smaller due to the smaller sensor size, should you want them.