Why no "Built-in" Speedboosters?

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Skyler King
Skyler King Regular Member • Posts: 156
Why no "Built-in" Speedboosters?

It suddenly occurred to me, why no built in speedboosters? Here is my train of thought; 
-With a full frame camera, you can make a 35mm lens with an f1.4 aperture and have very good image quality. 
-With an APS-C camera, if you want the 35mm field of view, you need to use a 23mm (roughly) lens. Of course, you usually still end up capped at f1.4 as anything larger starts to run into complications involving image quality (among other things). So, your 23mm f1.4 ends up being a full frame equivalent of 35mm f2. 
-This same issue occurs with micro 4/3. You can use the 17mm f1.2, but it is enormous, heavy, expensive, and ends up giving you (roughly) a 35mm f2.4 equivalent. 
-Many people have tried a very simple solution; Taking a full frame 35mm f1.4 and using a speedbooster/focalreducer so that they can use it on their APS-C camera and still end up with (roughly) a 35mm f1.4. 
-These speedboosters are 3rd party, and even the cheap ones from some unknown company in China yield surprisingly good results. Which leads me to believe that a major company with amazing optics prowess, like Canon, Nikon, Pentax, Fuji, Sony, etc, would be able to make a speedbooster that eliminates (or nearly eliminates) any reduction in image quality as well as any reduction in AF performance (when applicable).

So, suddenly, I arrive at what seems like a very obvious conclusion; 
When we see companies willing to disregard smaller form factors in an effort to make their lenses closer to the full frame equivalents, and they are willing to spend to much time and money on R&D, then charge so much for the resulting lenses...
Why don't these companies just make a full frame lens with a proven optical formula, and (essentially) just add what would equate to a "built-in" speedbooster? 
Their lens, their speedbooster, and permanently pairing the two together should result in the "full frame equivalent" with no reduction in image quality, no AF performance loss, substantially less money spent on R&D, and a resulting lens that is only slightly bigger than the normal full frame lens (rather than being 2x or 3x the size of the full frame lens, like we see with the Olympus Pro primes, for example). 
Does anyone have any insight on this?

 Skyler King's gear list:Skyler King's gear list
Nikon D3S Nikon AF-Nikkor 80-200mm f/2.8D ED Nikon AF-S Nikkor 24-85mm F3.5-4.5G ED VR +2 more
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