Stockton, I think you are getting WAY too drawn into the world of WWE. Vince didn't "Fire" J.R., at ANY TIME, well... maybe before 2000, as I don't remember much before then, but not in recent memory. Those was just Storylines, dog. Same with Bischoff, he's still (or was, may have run up by now) under contract.
Mordeci was yanked from TV because the dude playing him was still hella green, so they sent him back to OVW to brush up on his skills. He wasn't working out right, so they let him go. They later have him a second contract after he showed hella improvement in another try-out match. He went back to OVW to get him up to speed and await a gimmick, ECW rolled around and they repackaged him and we are where we are now.
Hassan was killed off for one simple reason. WWE fucked up and went with a Terrorist-esque gimmick and it just so happened to aired the same day as the attacks over in London. What was they to do after that? People paniced, they threw hate at WWE for the "Tastless Storyline", UPN made it WELL known they didn't want him on their network, if I remember right, Spike had the same feeling toward it.
Their only option would be to use him once a month, or once every other month depending. He could only be used on PPV's as neither network govern them, so WWE was left with the option of killing off the character and saving them the hassle of trying to work around it, and thus making the un-happy people happy again... or try to work out a deal where they had Daivari building the fued up over the months, with Hassan in the match at the PPV............... just WOULDN'T work.
The Kane vs. Kane thing was pulled off HORRIBLY. That played a BIG part in why it was nixed. Could it have been a great storyline? Yes. But WWE fucked it up from the get-go, and it got a bad reaction in the beginning.
As for who played him, no, it wasn't the same guy who played the Fake "Undertaker", that was a whole nother dude completely. That dude was (Thinks) Forgot his name, might have played the character of "Chainz" or something way back. He was also the guy who played the Fake Deisel (but I'm not to positive on that one), either way, the Fake Taker was also Taker's best man when he got married. The fake Kane was played by "Freakin' Deacon" who was down in DSW. From what I understand, the "Freakin' Deacon" gimmick is being tweaked, to prepare him for his Smackdown Debut.
Another Storyline that was dropped hella sudden... anyone remember WAY back when Goldust & Booker were teaming? Maybe it was shortly after. Booker kept recieving "I know..." letters (think "I know what you did last summer" typa deal), either Goldust was rubbing people the wrong way backstage and was set on his way out, OR Vince ended up hating the storyline and decided to nix it, don't remember which, it was one of the two.
Haha, damn... been a long while since I posted in here.
EDIT: Just remembered another fairly recent example of a nixed storyline. When they was building up Miz's debut, they finally had him show up to the arena and Palmer Cannon had him escorted from the arena, saying he wouldn't be on "His" show. They did this as the first step to building to a Palmer/Miz fued... but like 2 weeks later, Palmer said he quit and flew himself home from the overseas tour.