Donating spells.

We all know that donating troops to clan mates is really helpful. But what if you could donate spells too? I was thinking that when you upgrade your clan castle to level 3, it gains 1 spell slot. This way, you could bring the normal 20 troops that it can normally fit, along with 1 spell or 2dark spells (since dark spells take up half the space as a normal spell). There would then be 2 clan flags in the attacking gui. One with a sword symbol in the bottom right corner and the other with a potion symbol. The sword one would deploy all clan castle troops, and the potion one would deploy all spells(by potion I mean the shape of normal spells, it resembles a potion in my opinion). If you think this would be overpowered, really think about it. With a normal level3 clan castle, clan mates can donate Max level witches, wizards, and even dragons, which makes a HUGE difference on the outcome of a battle. So what would make spells so much different, especially since they only a effect a certain radius for a certain amount of time? It would also add something for town hall level seven players to burn elixir on. I have been at town hall seven for a long time and am nearly done maxing out my walls and troops. Since all that is left are walls and minions and hog riders, I have nothing but war troops and barbarians and archers for my loot farming army to burn elixir on. As a result, I have had full elixir storages (4,000,001elixir) for over a week. Since spells are rather expensive compared to troops, this would help to balance that without forcing players to rush their town halls.