Lanefan
Victoria Rules
Maybe as a feature specific to Arcane Trickster there could be a short list of thieving-type spells that, if up-cast by a level or two, can be cast somewhat stealthily. Depending on circumstance, observers still might get a check to notice you casting.This Arcane Trickster would like a way to stealth-cast a spell without advertising "Here I am and this is me doing it".
Whether sneaking up to a back door and using Mage Hand plus thieves tools to pick the lock, or casting Dancing Lights from behind an approaching foe to signal my friends to get ready for trouble.
What kind of penalty would counter-balance the advantages?
Maybe 'cantrips only'?