At the moment if(see_invisible>=invisibility) we can wee atom. I would request ability to use bitflags for these.
if(see_invisible&invisibility) then we can see atom.

How it can be useful?
For example owner wants players to see dead players, but not hidden monsters, while some other class can see hidden monsters, but not able to see dead players. With current vars it will impossible to make it (unless using image())
Things like this have been brought up many times; use the forum search. Since something like this isn't implemented yet you can deduce it is either rejected or on a low-priority