I found something pretty silly but potentially useful during K. Rool dittos. I tested this in training mode, K. Rool reflecting a diagonal upwards moving cannonball with his counter confirmed fires it back at the opposing K. Rool at a downwards diagonal angle flying back from the direction it was fired. It's situational, and we'd need to do more testing to see if the enemy K. Rool can vacuum in time, but the cannonball does come at them faster than when they refired it out. Dodging or shielding/parrying the countered cannonball seems likely, but also needs testing.
*EDIT* Cannonball is intercepted by platforms, but this maneuver can be performed pretty close to the edge of a stage. SOmeone with a wuick reaction time could reflect the cannonball, and if the opposing K. Rool vacuums, you have a quick moment to jump out of the counters end lag and reflect the cannonball at a much closer distance, possibly eliminating any chance of the opponent reaction to the counterplay.
*EDIT NUMERO DOS* Oddly, the reflected cannoball at a downwards angle seems to ignore the opposing K. Rool's vacuum, instead hitting them anyway. If an enemy K .Rool can't react out of neutral special's end lag in time, this could be a viable albeit still situational counterplay, and a hype maneuver to see in a competitive setting.