I hope you're just joking, a 28-200 f/2.8 would be incredibly heavy and expensive. Just add the 24-70 and 70-200.
I wonder if the 24-120 f/4 is relatively light, I wouldn't mind picking it up if the price was relatively reasonable, maybe $800 or so.
I'm not joking and it probably wouldn't weigh much more than the 70-200mm f2.8. The 70-200mm is 21 elements in 15 groups while the 28-200mm f2.8 patent is only 16 elements in 7 groups. Plus weight doesn't seem like a huge issue for many as they are willing to lug around a 200mm, 300mm, 400mm or a zoom in those ranges. Im not asking for the 600mm f2.8 they patented!
Admit it, if weight and price weren't an option most nikon shooters would prefer it over the 24-70mm and 70-200mm combo. I shoot with a similar combo (28-70mm and 80-200mm f2.8's) and find it a little cumbersome at times as there is always an extra lens to lug around and sometimes it just takes too long to change lenses in order to get a shot. I'm also pretty sure my 300mm f2.8 would weigh more than it.
With that mentality the first 18-200mm would have never been made. I started when people thought the 35-200mm f/3.5~f/4.5s was the largest zoom possible and now tamron has an 18-270 on the market...
The patent is here...