Here's one way to approach the task of making specific models visible or invisible through code:

Declare a synonym for each model, e.g.:
synonym syn_water_mutant {type entity;}

Declare a numeric variable for each model:
water_mutant = 1;

Put that same number into one of the first eight skills for the model in WED (let's say skill8)

Make an action that you attach to all the models with code that associates each model with it's synonym. (A single action script in WDL that would have an if statement for each model).

if my._SKILL8 == 1 {
syn_water_mutant = me;
}
etc.

This gives you a synonym for each model. Then you can write a function that you can call to change the visibility of all the models in your predetermined groups:

syn_water_mutant.invisible = ON;
etc.

Now don't quote me on the exact syntax of all this, but this should get you pretty close. Of course, the experts out there are bound to have different ideas about how to do this ... and I'm anxious to hear 'em. Good luck!

-------------------------------------------