The foliage tool currently has the ability to randomly scale your objects, let’s say trees. There is also the option to uncheck “Uniform scale” and allow the tool to randomize the height, width and depth separately, thus making some trees slimmer and other ones fatter.
However, this is not optimal. It works by giving a minimum and a maximum values for X, Y and Z (height) separately. So a tree can potentially get very high, and too slim for its height. It can also get very thin in X, but at the same time too fat in Y, this way making it very deformed.
It would be good if an option is included to make the possible variance in X and Y a percentage of the size in Z. Meaning that the possible thickness of a tree will be related to the height it got after randomization, instead of to absolute minimum and maximum. This way higher trees will be allowed to get bigger width to suit them, while short trees (Z) will be kept also smaller in X and Y.
Another nice thing would be to add a dependence between the sizes in X and Y (thickness in both directions). Very often you would want to keep the foliage instances non-deformed in the horizontal plane, especially if the trees are stylized and round, for instance.
I believe this would be a very valuable addition to the Foliage tool.