One of the big advantages of forming an alliance with another empire is that you can use each other’s colonized systems for “refueling”, often dramatically increasing the range of your ships.
Since the galaxy maps in ROTP already show the normal and extended range of your ships, I needed to modify that display to incorporate the borders of your potential allies.
Here are two screenshots of the Galaxy map from the Races section. You can now see easily how the ship range of the allied ships has been greatly extended.
The player’s empire (Meklar) selected:
His Silicoid allies selected: