I appreciate that :) Maybe something more like this.

Greed will have access to a dimension that is basically a bag for him/her. Greed can open this at will, and put anything inside it, or pull anything inside it out of it whenever they want. Greed could place whatever they wanted to in their and take anything from within it out at will. It makes sense too, what's better for Greed, then a bag where you can put everything you want into it without ever running out of space? The drawback would be that they have to actually "open" it by focusing on it and then actively reach in and grab what they want, the object wouldn't just instantly appear from this dimension, or when greed wants to put something in it wouldn't just disappear either.

For envy, instead of taking objects, envy clones them. Upon touching and feeling an object, envy can create a clone of it. It fits the theme, as envy doesn't want to take what others have, just have his/her own version of what others have.