Anti Assassin Trifecta solution: The Pool of Upgrades

What is it?
This is an idea that; while the two, four upgrade path was great, the late was literally just "Who can spam the Temple of the Monkey God" the most. While I know it's kind of a temple of a god, the strongest thing ever, that's boring. I honestly think stacking them sucks. Also monkey farms makes this way too easy. I just buy one factory, then I accidentally buy 30 temple of the monkey gods. Boring, right? Well, either one could delete it, or shape it into something else. By shaping it into something else, I'm talking about my philosophy to not nerf one guy, but to buff everyone else. That makes things crazier and more hectic, so fun! Thus, a key to fun is to instead of having the two/four path, monkeys would have separate upgrades, which could cut off others, or MUST be bought for another to work. For example, for the Monkey Apprentice, the fireball must be bought to get dragon's breath. However, if the Monkey Apprentice has ice breath, then he cannot buy the dragon's breath. Within that, there could be a bridge upgrade, maybe something like: A two handing multitasking Robo Monkey style upgrade for the Monkey apprentice, where he shoots ice out of one hand, and flames in the other.

How does this nerf the fast fire burst AOE assassin?
The temple of the monkey god would simply not be as strong, or as expensive. Use him, yes, do it, however, he shouldn't be the only one on the field. If his price was raised, no one would use him. What's the point of having him then? Thus, he would be nerfed by having competition, by having the dart monkey gain some amazing power, and then maybe the boomerang monkey could too, and all of the towers!

What is an assassin? What is a burster? What is a fast firer?
To me, the game works like so. Bomb towers are useful because they make a burst. They only poke through one layer, but will hit a whole wave. An assassin would be something that's for taking down moabs usually. Things like the Apache Helicopter, The Sun God, or the Sniper Monkey. All of them are really good for doing high damage. Fast firers are a subtier of that, which they pump out a lot of DPS, but only pops one layer. The thing is, the Temple of the Monkey God is -all- of them. He's just there to take down 1000 extremely close together lead/camo/regen Zomgs by himself. That's not supposed to work. Besides, that's no fun, winning so easily like that. In a way, he could be put into one of the categories of towers with the pool of upgrades.

Final Comments
This was my first submission, and I do hope no one else has thought of this in this way before. Otherwise, I made a big mistake, since this isn't original. Funny, since I think it's original. Even though it may easily not be. Also, if this is submitted and I did this right, then I'll post more in the monkey towers section.