There is no rule that, by RAW, explicitly prevents a player from shooting their own units aside from their own characters (must be the closes visible ENEMY unit, p. 179 CR). Additionally, while you cannot charge your own units, you can fight them if both are within fighting range of the same enemy unit.
If there is a rule or FAQ I have missed, please tell me.
I feel like the utilization would be very situational, but i guess you could have the Ynnari HQ's start eating aeldari if they were low enough in wounds, kill your own units to deny an opponent points, use 5-man wych/kabalite squads to fuel Strength from death, or force a morale test on your own kabalites of the obsidian rose to fire more darklance/blaster shots with "failure is not an option".
"The law of very large numbers: Given enough attempts, anything can happen."
"If brute force isn't working, your'e not using enough of it."