Dou you mean something like Ashe´s E but samaller? I thik it would make sense tematicall, and personally i love the idea since all her theme is about light, but not really necesary.
Q- absolutely no, Lux is a non mobility squishy champion, her Q cant be a skill that u can spam just to give vision, her Q is part of her core personality, you hit Q and u kill something, also, you fail Q and you are dead since is her only tool to scape from any danger, the lux player have to always play around her Q. What i mean is that would be an unnecesary change that wont affect ther current playstyle, after all, you always have to see where are you casting your Q so why add vision?
W- Well its a really wide and long range projectile, and basically would doesent have any repercusion for her if she spam W just to give vision to herself or allies, so it would basically mean she would have an small ward every 14s at lvl 1. A really long skill that would give her a lot of vision and safetly with not consequences for her.