IMO, you can temporarly give everyone nightvision ability. Because if it is too dark for people and they wan't it lighter, maybe as light as it is in rainy weather(probably not in PS yet) at day, then a night needs to look different.
I imagine nightvision as avarage lightness but with very low saturation, so every color is barely distinguishable. Is it that?
When we can have lanterns, magic, people could light up some larger area, so not everyone would need to have nightvison.
In general i believe a dark night when you can barely see anything is very immersive. Annoying, but adding to the game. Though if people don't want their characters go resting at a night and still see everything easly, maybe change the setting and let the Azure Sun shine all the time, or something? - that paragraph after we have light sources.
Sorry, about writing about the same issue yet again.