New Turncoat Troop - Name TBD
What about a Yuri type troop (like in command and conquer series).
Some kind of mystic that has very limited range, maybe surrounded by small cloud (like Pig Pen in from Charlie Brown) when getting close to attackers (or defenders) turns them to his helpers for a few seconds (10 sec at max lvl maybe depending on troop being turned).
There should be a balanced downside to using it , say the troops he turns (max 8 or so at top level) rage for 3 or 4 seconds after the effects wear off attacking the turncoat if they still live. Another downside could b he triggers rage effect in defending Barbarian King if the turncoat gets too close to him. The Archer Queen would not be affected. Air troops would only be confused and move away from the turncoat for a short time.
There would also be a limit of one per cc or attack squad.
You get the gist of it. It can be tweaked for functionality.