It would be super cool to limit the distance between them to zero so when you move IK target it cannot slide away from the joint into the abyss. Mainly it's useful when you change the rotation or location of the spine and IK targets throughout the body get lost somewhere on the way.
Sadly that isn't possible because it would create a dependency cycle. (Where the Parent depends on the position on the Child but the Child also depends on the position of the Parent - eek)
What I like to do is have stretchy IK, even on naturalistic rigs. The animator will need to control the limbs so the don't go crazy with the stretching but it's nice to be able to have the legs stretch to where you want them to end up. It's really difficult to animate a walk cycle and have to reposition the whole character just because you need the foot to go an extra 1 inch.
Hope that makes sense.
There will be more rigging content in the future ;)
Seems like using the Custom Shape Transform under the Bone > Viewport Display settings can keep the control bone in place without dependency cycles. For instance, setting the transform to the toe bone of that leg would visually move the control bone to the toes. Especially if the toes are mirroring the rotation of the control bone, it makes fairly intuitive visual sense.
It seems to work as expected with stretching enabled (I'm guessing, at least; stretching seems to do some wild stuff).
