Invisible mod?

The difficulty of it is if you make them truly invisible (like that mod Cupid linked mentions) you can't interact with them anymore. Can't click on them to do normal stuff. I've explored it in detail before, but the closest I could find to the possibility of being sort of invisible is: visually, making a sim into a ghost, and in terms of gameplay, making it so that the sim is excluded from as many social interactions as possible (e.g. for all intents and purposes, other sims "don't know they are there" because they can't interact with them). My Social Pariah Trait mod does the latter. Making a sim a ghost though is a different beast as you have to make them a ghost to get the translucent effect as far as I can tell, which means you risk tying them up in some ghost behaviors or restrictions, which may not be what you want.

But I don't mean to talk as if the mod Cupid shared isn't a good one. I haven't tried it, but it may be just what you want. Dunno.