Once your proportions are locked in, I recommend exporting a static mesh of these changes from the editor that the artist can use to line their source model back up to. Then, you can pass back to rigging for a final update.

Of course, for limb lengths, you need to get a little more creative and utilize the translation mode while also moving the pelvis to offset the change, like so:

As we run the game, we can tweak that variable live and it will keep once we're done running the game. Using this method, we can setup all sorts of variables: head size, hand size, arm length, leg length, torso length, character scale, etc.

It’s so nice out today! And I love these wind chimes