So, in the chat, we were discussing xenomorphs and what people think of them, what people SHOULD think of them, and how to make them scary again. A solution we came to (which Richard has mentioned as potentially viable) is a 'vision cone'. The dimensions and whatnot are entirely configurable, but the idea is people can only see behind them a single tile. It would not only make xenos and other sneaky antags a more credible threat, but also help predators pounce them (assuming they can still 'hear' emotes behind them.)
Potential con is griefing being able to be sneakier. Hence why I thought we could discuss how to implement this, or maybe some other way to make stealth more viable other than merely total-invisibility ninjas.
EDIT 1: One of the proposed methods for doing this is utilizing the sleeping screen darkening. Essentially, applying a large clientside image that leaves only a section visible.