There is another feature that would absolutely rock if it made it's way to MoI: Basic rigging. More like constraints, really, an ability to set MoI to always rotate and translate objects together whenever they are all selected or even visible at the same time.

One use case would be designing an object that should fit another, for example a laptop docking station. After making a "baseplate" with connectors that mate to the laptop, you could then manipulate it in space freely as the overall design develops without having to bother with moving the laptop at the same time. Yet, it would be instantly available at the right place if you had to check the design.