Add-on Abilities to Defenses, unlocked at TH10.

Many many people have requested countless new defense types- the dragon cave, the pulse tower, the poison dart tower, etc. However, the likeliness of these being implemented is low because space is already crammed in the higher TH bases (8-10). However, I have devised a way to add new defensive types, while the amount of space used up stays the same. I also think this would be good, because at the moment TH10 really doesn't get anything new except for a few final upgrades and the inferno tower (correct me if I'm wrong), and this would add a lot more interest to the game at this higher level. However, it is a quite a lot, so if there ever is going to be a TH11/12, then some of the more advanced stuff can be moved there.

In a nutshell, unlocked at TH10 as I said, there will be a choice of picking one or two extra abilities for your defense tower. There will be a visual difference to tell add-on 1 from add-on 2. Also, when clicked on, the tower will say, if you chose choice one, Mortar Level 8a, or Mortar Level 8b if you chose the second one. The add-on will take time and gold, but beware, because once you have chosen one and the upgrade has been finished, that tower is stuck with the one you chose for it! So choosing wisely is necessary...
I have several examples coming up:
(Note: I will not have any cost or time listed, because I am not that far in the game yet, and I don't know what is balanced and what isn't)

Mortar:
Choice 1: Blind spot is one tile smaller, so it does not reach over directly adjacent walls anymore.
Choice 2: The shell is slightly seeking, so it will target fast enemies like goblins and archers more easily.

Wizard Tower:
Choice 1: Each bolt inflicts slowness on all the troops it damages, maybe 30%? (does not stack, that'd be OP)
Choice 2: Each bolt explodes with an aura that eliminates the rage spell effect.

Tesla Tower:
Choice 1: Immune to lightning spells, grants 25-50% immunity to the towers in it's range.
Choice 2: Any enemy attacking it will be slowly and slightly hurt, because of the electrified surface.

Those are just examples, as I said. There will be two like these for every defense tower (but not traps and walls!).
To balance it out, you can also give these add-on ability choices to troops, too. When a troop is at it's highest level, and you select it in the laboratory, you will get the choice to upgrade it to 'a' or 'b', just like the defenses. Also juts like the defenses, you get a description of each upgrade. Here are examples-

Barbarian:
Choice 1: When used in a group of 50 or more, a 10% damage increase takes place for all barbarians- an addition 10% will also happen at 100+
Choice 2: Barbarians have a 20% immunity to splash damage towers.

Archer:
Choice 1: Bow range is increased by either 1 or 2 (haven't decided).
Choice 2: Are much cheaper in training cost (if you use archers a lot, it will eventually pay off).

Baloonian (Balloon Bomber):
Choice 1: Bombs dropped do more splash damage.
Choice 2: Bombs dropped will trigger un-triggered traps (without damaging the balloon of course).

Again, these are just examples.

I hope you liked my ideas! Constructive criticism accepted.