Before I contribute with my convoluted mess, I will just say I really like khawk's idea of a Jim Brunzell return in 89. Dylan's idea of Tajiri as ECW champ is definitely better than a Justin Credible reign.
In The Undertaker's last real run before becoming a WrestleMania attraction, he disappeared due to a "mysterious" attacker and Kane went around for a while searching for the attacker before revealing that it was him. Before they did the Kane reveal, I thought it would be a neat twist to have them reveal Luke Gallows as the other son of Paul Bearer, the half brother of Kane. He even had the back story as fake Kane which he could reveal was his first attempt to attack The Brothers of Destruction. My original idea had them sticking to the kayfabe death of Paul Bearer, but he ended up returning so they could have even had Paul Bearer be the guy behind it all, looking for revenge against The Undertaker for "killing" him and Kane for not avenging him.