It would be great to be able to scale and position elements relative to a bounding box or another design element. Kind of like a canvas inside the main canvas. This way you could position and scale the bounding box and have any connected design elements move and scale automatically with the bounding box.
To be able to position x and y by percentages of the bounding box dimensions would also be a great addition.
This would allow you to import designs to different sized products without having to manually resize and position each design element. Just change the size of the bounding box and all of the elements change move and scale automatically.