Want FX but not impressed by D800 build quality

There are at least three 'build qualities'.

1) The 'feel of the camera'. This is entirely subjective, unmeasurable and unadvisable. While you have every right to feel that the 'feel' of the D800 is worse than the D200, that is an entirely personal feeling, and thus it is very hard for anyone to tell you if any camera would 'feel' better to you. Maybe if you tried to articulate what your feelings are based on, it might help. If you have 'the sense of plastic' it is likely as anything just the paint finish that Nikon has chosen, ore eles the improved, higher precision (more plastic like) castings.

2) The strength, robustness and sealing. Since no manufacturer gives out any sensible information on these, and no-one does any rigorous testing, it is impossible to tell if any camera is any different from any other.

3) Construction principles. Here, the D800 and D200 are exactly the same. Both have a magnesium alloy monocoque body construction, such that the metal chassis forms most of the outer of the camera. The exception is the front cover and the flash assembly, which is polycarbonate on both cameras.

Here is the D200

And here is the D800

Really, no difference between them at all. I think you just need to learn to think of the D800 as being the same as the D200, and you'll be OK. The D800 is the cheapest FF DSLR you can buy with a metal chassis, so there is really no alternative if you are looking for something built like the D200 (which it is).

--
Bob