Change mechanics to be more like illusion. As in be able to mimic the same languages the character has.
Be able to Mimic Ability Stats, as the Character has.
Remove Armor penalty, as it does not use the bonus. This creates issues with final AC. This at most would increase the AC of non cloth wearers a few points.
Currently the Shadow is way to easy to spot as well. The Hide/MS does not match the character.
Attempting to use the Shadow as front line RP, and shadowing the shadow is difficult, with Ability points being seen, no languages, and no walk.
So overall more control over the Shadow would create a good amount more Shadow RP.