Need Help in getting Aura-Emitters to stay put

[Chazar]

I thought that Bodyguards dont count with respect to the order "stay behind troops". Hence you must set apart another unit under his command, which is not set to "guard commander"...

...but then this wouldnt help again, since this unit would have to be ordererd to hold and attack OR fire. So you could sacrifice an archer every once in a while, which is ordered to fire and is placed somewhere near him...