Even though it conflicts with what we use to consider as being good advice, I found a feature in AX 2012 that will allow a user to change the contents of SYS labels.
It is of course interesting to investigate how it is designed, even though we'd usually discourage changing SYS labels. You can find the feature under Product information management / Setup / Dimension groups / Product dimension groups:
The class behind the feature is EcoResProductDimensionRename.
This will not work from an application controlled with a Version Control System, as the code doesn't do anything to try a check-out.
So, why is this maybe not such a good idea? One of the main reasons is that the labels will change back to standard at the next major release upgrade. See https://msdn.microsoft.com/en-us/library/aa678556.aspx for recommendations on not changing SYS labels.