I dont have dark elixir but i think that is a good idea
In my opinion, this trap should be able to affect up to 15 housing space of troops. For example, 3 giants, 15 barbs, 3 wizards, etc. The trap would be similar to the spring trap, 15 housing space worth of troops have to walk over the trap to be affected.
I also say that troops more than 15 housing space and troops with no brain are not affected. If the "no brain" part is too complicated, SC could just have the 15 housing space part. Pekkas, golems, and (maybe) wall breakers would not be affected. The bewitching trap should also be upgraded to affect more housing space.
Your idea for witches, in my opinion, is too complicated. Either has witches affected as normal, or not.
Question: Does the bewitchment have a time duration? Or are troops affected until killed?
The lvl one version is ok but then it just gets OP