Yes, I'm posting another thread that specifically covers one potential guest character in particular, so if it bothers some purists, well, can't please everybody. Don't worry, I'm not about to post dozens of individual guest threads all at once, nor everyday. And I don't care about copyrights, or how unlikely we are to get certain characters as guests. Now, with that said...

Variants for Jason

Undead: The best known version, from Jason Lives to Jason X, before he got upgraded. He is slow, can barely jump, if at all. However, he barely flinches from most attacks, and has boss-like endurance.

Human: the version encountered in the third and fourth F13 movies, and the reboot. Has the same endurance as the undead version, but he flinches from attacks (he'd grab his balls if Johnny low blow'd him), moves faster, and has better jumping prowess (though not exactly acrobatic).

The Jason X design, and the very first one (the potato bag) from the second movie, should be alts for the undead and human variants, respectively. The JX alt should come with a aesthetically-different machete.

Intro: Kobra, with a machete in hand, prepares for the fight, when the ch-ch-ch noise is heard, and Jason, suddenly behind Kobra, kills him (in a variety of ways) and grabs his machete. Alternately, Jason could already have his machete, and kill an MK character (but not any bosses) who didn't make it in as a part of the roster, and/or Freddy, if he too didn't make the cut. "Conversations" between Jason and the opponent would obviously be one-sided, but you'd still see Jason react, in some ways.

Fatalities (just a few)

Crystal Lake: the fight would take place near a lake, with a canoe on the water. The stage fatality sees the opponent uppercutted in the canoe, followed by a young Jason coming out of the water to drag the victim down.

Choke: Grabs the opponent by the throat, and strangles them to death. The camera should focus on the victim's face as they are getting the life choked out of them. Once they die, Jason violently drops the body.

And, the best for last

X-Ray: Pulls a person wrapped up in a sleeping bag out of nowhere to knock down the opponent and beat on them. You'd see both the opponent's bones, and the victim's, being broken. It would end with Jason kicking the opponent away, and throwing the victim at them.