Are you basing that on actual info deconfirming them, or just making an educated guess due to it being based on a rather stupid rumor to begin with? (Which I agree with, but the clues recently dropped by NRS about their DLC plans mesh disturbingly well IMO).
If its a returning character assuming Boon wasn't trolling I am curious who this big brute character will turn out to be, as that description seems to rule out the most likely candidates like Tanya, Cyber Smoke, Fuijin, and such. Reiko's kind of a meaty guy, but his move set hardly matches the style of a heavyweight type character. Tremor fits the build and has the cult demand, but Boon has repeatedly stated he won't be appearing.
Also a MKO member recently tweeted Paulo Garcia about Cyber Smoke and got this reply: "if u get 2mil ppl to buy the dlc season pass, I'll stop what I'm doing and make Cyber Smoke.", which seems to deconfirm him.
As for crossover characters in general I wouldn't be ruling them out. Yeah the hardcore community that tends to frequent MK forums would mostly be outraged, but the general masses would likely be thrilled to use a slasher villain, famous badass game character/celebrity, etc. Unfortunately a character like Jason would likely be more profitable to release then even a popular member of the remaining MK cast.