I stumbled at a feature which is seemingly easy to implement but of high importance for many developers. As far as I know: no IDE supports it yet:
If you develop in packages you don't want your packages to cross reference to other packages, this is especially critical if you work with different source folders. One referencing to another is okay but as soon as there is a reference back its a terrible problem. This tends to become even more difficult to figure out once its not just for two packages but if package A refers to B, B to C, and C back again to A.
Anyways: I think it would be of huge help if it was possible in typical FDT manner while typing to see as error if you are creating a cross reference.