I'm actually planning on making such a script for a mission this weekend.
Basically I'll keep looping a findNearestEnemy every 10 seconds, and when the enemy FO discovers an enemy, it will create a fire mission template based on the enemy position. Depending on daylight the script should chose for ILLUM or HE.
I have no idea if this is gonna work well, since scripts relying on BIS AI usually end up kinda dodgy, but I'll let you know if I have some success.