What if the ABA never happened

People would have definitely been more annoyed by Taker, the gimmick change made people ignore how out of shape and bad inring he was during the first year or so of the ABA. He was already transitioning to this character before he left in 99 too.

It's weird to consider it, given that it was only a 3-4 year stretch, but I feel like there's a possibility that just doubling down on the Undertaker's longstanding gimmick could have potentially come to be detrimental to the way his overall career would one day be looked upon. It's always been a bit of fun contention because I always liked the ABA and I have a friend that vehemently didn't. I feel like, in addition to just being plain fun (at least to me), engaging in such a drastic shift from what he'd been doing up until that point bought him a new lease on the character. Absence makes the heart grow fonder, and I think the overall result of holding back the "vintage" Undertaker for a period of time did favors across the board.

That's what Nash said, he was trying to get Taker there for a while but Taker was loyal to Vince and the WWF. However, he said that Taker was not liking some of the things that they were doing in the WWF and what his role was, which is why he probably reached out to Nash in 1999 when Nash was the booker. Then again, Taker could have reached out to WCW as a way to leverage Vince for things Taker wanted (more money, different character).

I still feel if Sting came in during Invasion, Taker would turn into the deadman again.

Let's be honest Taker in 97/98 was pretty much human so it wouldn't have really made a difference if he reverted back to that persona after his Lord of Darkness run.

His only real downfall during his biker gimmick was his ring work. 2001 was possibly my least favourite Taker year. 

Agreed. When he first debuted the ABA gimmick in 2000, I actually kind of liked it. Nothing will ever beat early 90s Undertaker in my opinion, but the character had grown kind of stale so it was refreshing to see him get such a drastic overhaul.

However, like the OP mentioned, I don't think I've ever cared less about The Undertaker than I did in 2001. He was prominently featured all the time, but I was over the new gimmick already. It didn't help that he was gaining some weight which affected his in-ring abilities. However, as bad as that stretch was, once he turned heel at the end of the year and cut his hair it changed everything. That may be one of my favorite Undertaker runs ever which says something because I'm biased towards the Deadman gimmick. Undertaker as a cowardly biker bully just worked so well.

2002 was one of his best years if you ask me, but once he turned face again that fall I lost interest for the rest of his ABA stint. So to sum it up, I initially liked the character because it was different, but looking back I think it was most effective when he was playing the bad guy.

And to answer the original question, Kid Rock probably wouldn't be in the WWE Hall of Fame without ABA Undertaker.

We would have never had this fashion moment:

I bet Undertaker loves this shot.
Also, I wonder how many snakes had to be killed to make those pants.

Couldnt the Undertaker have went into a department store and bought a pair of black jeans?