Do you know if it's possible, for a player, to view or not a texture or a shader (I'm not technical, don't know what is the difference)?
We can use an already exist texture (or whatever) on something, and calculate a variant like in grey/green or grey/red from this texture.
And, this new texture can be visible only by Aliens in low light, or by H with helmet. May be when compute the texture we use the light level to se the transparency for this texture, with a little glow. Needn't high definition.
We already have something that make navmesh, why not this too?
And, if it's implies to change the map and it's not compatible, will be a problem for few map only, isn't it?