A Hellcat tank destroyer would be a killer addition. It would add a new dimension, and be difficult to use. It is fast, and hits real hard, but has light armor, making it a one shot ride, if a tank gun hits it once, its likely pretty much done. It requires a very different philosophy of operation than just rolling out a tank and swapping shots. You'd need the discipline to learn to hit with the 1st shot, and to MOVE if you didn't.