re: Could Raven have been a top heel in WCW after the NWO?
I think it's possible but a few things prior to that would have to be changed, such as:
1. The Raven vs. DDP feud ends at Spring Stampede with the Bowery Death Match, debut of Horace and Raven winning the United States title.
2. They began the Goldberg/Flock angle prior to Spring Stampede (where Goldberg faced Saturn). Instead of that, always tease Goldberg vs. Saturn but at Spring Stampede, make it Goldberg vs. Van Hammer or another member of The Flock who won't be hurt by getting squashed. As Raven said Kevin Sullivan told him, "Some must die so that others may live."
3. Goldberg vs. Raven is planned for Slamboree but Raven "injures" his ankle at Spring Stampede. See, if Raven's gonna be a top heel post-nWo, he can't wrestle Goldberg at this time. Using the injury angle and allowing a member of The Flock (Lodi, who was the kiss ass of the group) to defend and lose the belt on his behalf protects him, continues to build Goldberg and plants the seeds for the eventual break up of The Flock, via Saturn losing to Goldberg at Bash at the Beach (BTW, Goldberg doesn't face Hogan until Starrcade) because The Flock wouldn't (and couldn't) help him.
4. Between July and September, slowly break up The Flock. Saturn is able to set everybody free except for Lodi (who's the WCW version of Stevie Richards, based on his loyalty to the Raven character). Also, Kanyon joins Raven. So, at Fall Brawl, Saturn beats Raven to free everybody except for Lodi and Kanyon. They, along with Raven, are off TV until December.
5. The night after Starrcade (where Goldberg beats Hogan), The Flock randomly return to sitting in the front row. Meanwhile, you have the Goldberg/Bigelow angle, with Bigelow not being recognized as working for WCW. They show a recap of Goldberg beating Hogan, which Raven interrupts. He cuts a promo about Goldberg being the dominant force in WCW and beating Hogan, Sting, DDP, The Giant but "What about me? What about Raven?" He says while Goldberg won his United States title, he did it by beating his "lackadaisical lackey", Lodi (who Raven pushes, as he says it). And since Goldberg has new gold, it's time for Raven to get back what's rightfully his. He wants a United States title match tonight. It's time for the match but it never starts, as Kanyon and Lodi try to fight off Goldberg. Bigelow shows up, attacks Goldberg and joins The Flock as Raven's new enforcer. What this does is rebuild The Flock but more importantly, it's the first (perhaps second) time Goldberg has been vulnerable.
The idea of Raven being a top heel is heavily dependent on him having lackeys to protect him. That's the main reason the character was so good. The Raven character surrounds himself with people he feels are inferior to him, which allows him to control them and have them do his bidding. That way, it's easier for him to get heat not only because the Raven's Rules concept opens the door for heelish fuckery but the fact that he's taking advantage of the "lost souls" that worship him. Again, "some must die so that others may live." Raven's using these guys. That's what got Stevie, Meanie and Nova so over in ECW.
The trigger should be pulled the minute Goldberg leaves to shoot the movie in May. After the Goldberg/Bigelow feud ends, Raven moves on because he's got his belt back. But that's not enough. Because the fact that Goldberg won the US Title in the first place took Raven to a very dark place. So dark, that he called a former heated rival in Hak (The Sandman) to help him avenge the emotional pain brought upon by Goldberg stealing his title. Now, it's time for payback and the night after Slamboree, The Flock attack Goldberg. He fights them off, Raven DDT's him. He no sells, sets up to spear Raven but the lights go out. When they come back on, Raven is on his knees doing his signature pose and behind Goldberg stands Hak, who canes the shit out of Goldberg. Raven ends up "injuring" Goldberg's arm, which is the storyline exit for Goldberg, who also gets stripped of the World Title.
Raven wins the World Title and when Goldberg comes back, it's hell to pay.