If you opt against Glamours, you should probably given them something relating to their ability to hide incredibly well. Either something along the lines of Self only Veil, a variation on the Cloak of Shadows theme, or a power that allows them to use Stealth even in plain sight (ie, no penalties for 'terrain' or movement when using the skulking trapping). (Combined with a reasonable Stealth skill and Diminutive Size, this would be seriously stealthy.)