My opinion is , different sizes of balls are just a piece of "uneasy to use"
assume you have a image of your dream building in your mind and now you want to create it in Ylands. these are your steps
1. I want a certain shape
2. I need to find an "item" in ylands which is similar to the shape I want
3. if there's no such item, then I need to figure out: how to “put" other blocks together to generate such a shape
you will see there's 2 difficulties here
1. I need to be familiar of all ITEMS in explore mode so that I can find the thing I need
2. I need to figure out how to "put" things together to generate the shape, and here I also need to be super familiar with all items
so, why don't give us some basic shapes, like cuboid, cylinder, sphere, cone,etc... plus, sizeable
then it's perfect!