If you use the Darth Malgus Holostatue or the republic version, then you can activate any of the abilities requiring a companion out. You can do this trick with either the imperial or republic holostatue, but obviously as the tooltip says you have to be the same side as the statue to use it as a trainer.
Once your statue is out then you can activate any ability that requires heroic moment. This includes sacrifice/unity, heroic moment, and any class legacy abilities you may have unlocked. The holostatue only has a 1 min CD, so you are more limited by the CD of the ability you choose to activate. I am not sure if using unity shares a cooldown with your class heroic moment and/or a legacy ability, but this allows you to use these abilities during warzones and operations. Note: unity is the ability with a 5 min. cooldown that makes you take 50% less damage for 15 seconds--quite OP for warzones and useful in pve especially for tanks.