I assume some of these wrestlers you have in mind that you feel like nominating which include Sting, Harley Race, Shark Boy, A.J. Styles, Jerry Lynn etc. are all up for debate on whether they should participate in this contest or not. Not any of them have actual wrestled before the WWF was changed to the WWE for legal issues.
I'll go ahead and allow these wrestlers in for nominating in the contest if only because ECW and WCW were never necessarily companies that competed with each other with the WWF/E back in the day for better ratings or what have you.
They would sometimes have specials that would come on live television sometimes just to mock around with one another with the right for some episodic specials that came on that had WWF competitors compete on WCW shows and the same for WCW competitors on WWF shows. In particular the Survivor Series 2001 PPV standing out as an example for this.
In other words sure you can.
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Tom Kenny. The best voice actor alive today.