However, I think if he shed the Deadman character it would at least be different enough to fuel one last match. If he said last year was Taker's last match, this year is Mark Calaway's last match. Do one last go with his real persona of "BikerTaker" and do some awesome demon, fiery biker entrance at WrestleMania.
They could go even further establishing that this is his last match ever…announce him for Hall of Fame 2019. Bringing in Kane into the storyline as Taker's long time friend Glen Jacobs and the one inducting him a year from now could add more real aspects into it.
It's not ideal but it's different enough to garner interest in it, far more than the tired old mythical Undertaker crap.