How do I make a "slot-based" status effect system?

Heya, I'm the dev of a Point and Click/RPG hybrid game called Terry Rose (I hadn't released a demo yet.)

I'm trying to "revamp" my Status Effect system... And to keep things simple, only one person/creature in a battle can have 3 status effects at once.

I tried it so that once the "status effect" is put on a foe... An icon above their head will appear to show what effect they have (Like 2 Zs for Asleep, for Example.)

I'm just wondering if it's possible...

My approach would be to have an enemies family with a family instance variable for each status type, could be boolean true/false for all statuses or if it stacks like the game design is to add more of a status such as poison then you can use a number. Then for example if sleep is true then it has sleep, or if poison is above 0 then it has an amount of poison. This would link into logic for showing icons too. To count the total you could just add 1 to a variable for 'total statuses' and remove 1 when it is removed and if it is at 3 then don't apply more statuses.

Well, I use Number based instance variables since an enemy in my game is immune to certain status effects...