The question is at the very bottom. If you understand Buffs/Debuffs in tower defense games then you should skip the bulk of this question and go to the bottom (seperated with the long line)

I plan on making an IPhone TD game. The fact that its an iPhone game isn't relevant but I am coding in Objective-c with Cocos2D.

I am relatively inexperienced in the field of game design so I'm looking for some advice from someone experienced in this field.

In tower defense, there are two things that are relevant to my question: towers/enemies (both have their own classes/children). They each have stats like hp, damage, speed, etc.

I want to add buffs/defuffs, for instance: Towers A,B and C each have 15 base damage. Tower D would be a buff tower with no damage, a tower with an AOE(area of effect) aura that gives 10% damage to all towers in range. Tower E might slow enemies in its AOE, a debuff. Stuff like that.

The same could go for enemies. Enemy A is a boss that has a slow aura that affects towers and slows their base attack speed or something along those lines.

So the question is, what would be the most effective way to implement this? If it was just towers then I would just mess around with the tower classes, but since tower classes and enemy classes are both affected, should I make a buff class?

TD games can consume quite a bit of memory with large amounts of creeps and towers, and buffs I feel like would also consume quit a bit... So I'm trying to be as effective as possible.