Brian W. Allan

This would be near useless for me and most folks I work with. Any modern production lens will resolve enough detail to keep you from getting a pink slip. I wouldn't project some lenses 40' tall but for youtube or even broadcast I would rank a lens' resolution numbers near the lowest of important characteristics for my uses as a cinematographer. The overall aesthetic performance of a lens is what matters, followed closely by ergonomics. The former is not something a lens review will tell you much about. You might be able to spot some bokeh and vignetting characteristics, but short of renting it and pointing it at a person and looking at them in a few sizes you won't know much about a lens. The only reviewer I see doing any work like this is Lloyd Chambers of Diglloyd.com: his in-depth reviews, aperture series, and expert commentary are worth every penny of his subscription costs.
When the Sigma art 35mm 1.4 came out I rented it for a comparison to my beloved Zeiss ZE 35mm 1.4, and yes the Sigma could have an edge in resolution in some scenarios, but the Zeiss trounced it in terms of pure image harmony. Switching blind A/B on the monitor my crew all settled on the Zeiss. Just goes to show you DxO mark resolution numbers should not be a huge consideration in your purchases unless you are in the business of photographing and making reproductions of test charts.

I'm going to go ahead and say that the average consumer actually doesn't really care. They buy based on numbers because in their mind higher megapixel = better. They have no understanding of why, or how - but that's the thought process.
If you showed an average consumer a picture taken with a $100 kit lens, next to the same picture taken on the same body at the same focal length with a $1200 lens - they may or may not see much difference.
But they're unlikely to go out and spend an extra $1100 on a lens. Most consumers are baffled when you tell them a single lens can cost $100,000. 
Professionals buy expensive lenses because they appreciate and understand the very reason they're expensive. Professionals (and even enthusiasts, I guess) care about the quality of all the components, because they know the difference it makes to the picture.
Consumers don't get it. Realistically, someone who's just picked up a camera is unlikely to take amazing photos even if they have a $1200 lens on it.  

Could not disagree more. It would be the second coming of the Megapixel race in pocket cameras for dumb consumers.
I give you an example as to why. Say you have a lens thats listed it as 40 mp on it. Yea it may resolve that, but hows the image? Bokeh? Chromatic Aberration? When sharpness becomes the main concern for manufacturers (more than it is now) then we all suffer creatively for it. 
As someone that uses Cinema glass on his GH4 you know that resolution is not the most important aspect of an image :)

I'm sorry to say, but i think it's a terrible idea. We know how the consumer operates, people would then only look at the this megapixel count, as they already do with cameras. It's already not a good thing with cameras but it can make sense i guess sometimes, because it can be important. A lens is sooooo much more than its  megapixel resolving power. Besides, most people actually don't care enough to really mind if it has a high resolving power or not. Like you said, a lot use the kit lens and they're very happy with it, it's good enough for them and the may not want to spend any more money on it. The few others who know enough about lenses, optic, and photography in general to really be interested in this matter, also know enough to go look for reviews, test, advice, photos on flickr etc...
Plus, people would always ask "how many megapixels does that lens resolve" without know anything else about the lens, only focalizing on this, when everything else about a lens is so interesting and important. And to conclude, i guess MTF charts are there solely for that purpose.

​MTF charts published by lens producers are already greatly reduced in complexity, in that in general they only show contrast for two spatial frequencies (usually 10 and 40 lp/mm) and two aperture values (usually wide open and f/8) and two image plane orientations (sagital and tangential). The "full" MTF is a four dimensional quantity which is difficult to represent in 2 dimensions. I put "full" in quotes because it also depends on focal length for a zoom lens, and, to an extent, on the focus distance thus it can be a six-dimensional object.
I hope you can appreciate why it's impossible to boil a six-dimensional function down to a single number. You could simplify it further and measure the MTF at a few distances from the image centre (centre, top/bottom edge, left/right edge and extreme corner), but it's been heavily simplified already and that would cut a lot out.
You could try averaging the figures but the range you average over would be fairly arbitrary and subject to differences between manufacturers. And the idea that manufacturers attach a resolution figure to the lens in order to sell them would just open the flood gates to clever ways to inflate the score by carefully choosing what to include/exclude.

Nikon has golden rings, canon has L letters, sigma has the art series...
I would prefer instead for the average user to use their brain a bit better than have a company find better ways to "advertise" their products.

No they really shouldn't. A lens does not "resolve 6MP".
A lens renders a certain spatial frequency at a certain contrast ratio. It might take detail at 20 line pairs per millimeter and produce 70% contrast, detail at 50 line pairs per millimeter results in 30% contrast etc. This relationship is captured by the modulation transfer function (MTF), a quantity which varies according to the distance from the image centre, and the direction you measure in (sagital vs tangential). Manufacturers already publish MTF charts for their lenses, which is the equivalent of what you're suggesting, only much more meaningful. There are some differences in how these charts are computed (e.g. whether diffraction is included or not) so they're not always directly comparable, but they aren't anywhere near as misleading as trying to attach a single "megapixel" rating to lenses.
The other reason stating "this lens resolves 6MP" is meaningless is that the important thing in determining how you images will look is not the lens MTF itself, but the system MTF. The system MTF is the product of MTFs of each part, the lens the filter stack and the sensor (and image processing to an extent). Because it's a mathematical product (a lens delivering 80% contrast combined with an AA filter that delivers 95% contrast results in 76% contrast (0.8 x 0.95 x 100)) you can improve the system MTF by improving the MTF of any component in the system. Hence you "6MP" lens will give you more resolution on a 24MP body than on a 6MP body.
 
It's exactly this thinking that leads people to declare that there's no reason to have a 50MP sensor as there are no 50MP lenses in existence. Even the kit lens in your example produces some contrast in the centre of the image at 50MP.