You've always been intended to be able to scale your items, and the functionality is there, but for some reason the option just didn't appear. However, you can inject this code via your browser's console
on the page where you equip and adjust gear to make scaling functional.
Thanks to @rtsmarty for finding the issue. This will likely be added to the site natively very very soon, but if you simply can't wait here is the solution.
And a very special thanks to @Spritanium for the kickass update.
Code:
(function(i,n,j,e,c,t,css){
css=i.createElement(n);t=i.getElementsByTagName(c)[0];css.href=j;css.rel=e;
t.insertAdjacentElement('beforeend',css);})
(document,'link','//code.jquery.com/ui/1.11.4/themes/redmond/jquery-ui.css','stylesheet','head');
Thanks to @rtsmarty for finding the issue. This will likely be added to the site natively very very soon, but if you simply can't wait here is the solution.
And a very special thanks to @Spritanium for the kickass update.