Quick idea that I had:
If friendly artillery is set to fire it will likely fire into friendly troops / buildings if a fast unit such as a raider gets too close.
This causes often more damage by friendly fire than the enemy unit would have caused.
I had two ideas how this behaviour could be avoided, so please let me know what you think:
1. (Artillery)-Units can be set to avoid firing at enemy units that are too close to own units. This could be set with a distance variable to account for different explosion radius.
2. Artillery non-target zones. The player could set zones that artillery would not target, e.g. back or close to sensitive buildings (fusion etc.).
The behaviour could be manually triggered if wanted by the player.
So please let me know what you think.