This sounds like a really good idea. Now, if they would just add all the plus sizes to it so we could tell if a Lane Bryant 4X is the same as a Liz & Me 4X is the same as a Cathy Daniels 4X (from experience, they aren't all the same). It's one of the main reasons I don't like shopping online, unless I've actually tried on the particular brand and know how it fits. I know I can wear a 4X in Liz & Me from Catherine's, I have a lot of them in my closet (bought in the store and online). But most Cathy Daniels tops are too short (for my taste, anyway) and the proportions are off on me. Lane Bryant, well, nothing in the stores I like, and the catalog, I haven't ordered from them because what's in their catalog isn't in their store, so I can't try before I buy. I'm not about to pay shipping and handling for something I can't wear and then have to pay shipping to exchange it for another size that may or may not fit.
And when it comes to jeans/slacks, forget it. Most of them, I need talls for the legs to be long enough, but when I buy talls, the waist in front hits me just under my bra band. Average length is too short in the legs, but the waist in front is still too high (I must have more ass than belly, because I can tell you the only way the waistband would hit me at my waist is if I was nine months preggers). Depending on brand, I wear anything from a size 26 to a 32, and going by the measurements on their charts doesn't do a whole lot of good (RightFit is a prime example of this, the chart says I'm a blue 10, but I ended up buying a blue 8 in average length since the talls were about 8 inches too long).
What I really wish would happen: Clothing designers/manufacturers would get together and say ok, a size 0 is this set of measurements, size 2 is this set, size 4 is this set, etc all the way up to whatever the largest size is (60 or however high they want to go) and these are going to be the measurements for every garment made from now on. And then the manufacturers need to get on QA's asses to make sure that the people who are doing the actual sewing aren't making the seams larger or smaller than designed (and this happens, I worked in a garment factory and saw it every time we were pushed to do more faster, quality goes down the drain when it's quantity that's demanded). But that's a dream world, sad to say.