Nikon 18-200mm vs 80-200 and 18-70
I have the 18-70 and 80-200 one ring, but I confess (don't tell anyone) the 80-200 gets practically zero use, mostly due to it's weight and lack of VR. But I was surprised to find just the other day that about 25% of my pix are with the little 55-200 VR, which weighs practically nothing. I did some rough and ready testing between the two teles in bad light and even though the big lens has a two stop advantage, the wee one with VR beat it hands down. The 80-200 is still fab in good light though. My 18-70 does the job, though the zoom ring is a bit stiff, they really are a great lens with the only downsides being distortion and vignetting, neither of which trouble me greatly.
A few years ago I actually bought an 18-200 to save lens swapping when under pressure, but I didn't really care for it and when the AF turned out to be faulty, I had no regrets returning it. If you could get the 18-200 without losing your two classics, that might work, but I'd recommend adding the very inexpensive 55-200, just make sure it's the VR version. Have fun.