If you reverse pickpocket the arrows you want to the guard, then wait until his shift ends at 8pm, you can follow him to the barracks and pickpocket the steel arrows away. Thus you don't have to have level 100 pickpocket. You do have to watch out for a guard that wanders in the barracks, and have to look via pickpocket to find the right guard, but it is very doable, even for nonsneaky nontheif types. Not my idea, just saw a vid on youtube that showed it, and the guy had no level in pickpocketing, and not very high in sneak, so does work.