My local group has the opinion that disallowing SCs is the equivalent of disallowing specific units. The written "rules of play" we have says, and I quote (post translation):
"Special Characters are always allowed, as we do not believe censoring your army book or codex will lead to a more balanced game. To us, it is the equivalent of banning any other unit, like White Lions, Cannons, or Demon Princes. Keep this in mind before complaining about your opponents SCs!"
I sorta agree with them. Balance isn't perfect to begin with, but it would seem odd to ban a special character who, despite how powerful he might be, is still just 1 guy with a high price-tag, where, say, Banner of the World Dragon grants some obscene buffs to an entire unit of relatively cheap and brutally powerful models, including any characters.
Trying to balance the armies by disallowing SCs is a slippery slope.
I do enjoy making my own characters though, and being the writer I am, I like coming up with huge backstories, especially for the oldbloods. That said, I'm a bit annoyed by the fact that the special characters generally have abilities I'd really like on my custom characters, but can't.
Granting stubborn can be done though, which is why i've rarely considered using Gor'Rok. He's cool and all, but he is just too squishy, even with T6. His ability "Resillient" is also pretty meh on a 2 wound model. He is a cheap way to get stubborn though, a scarvet would cost 115 points base for the same ability, without T6 and any of his other nifty abilities.