as I understand it, there are parameters for what is a L&C fic and if you deviate to much from the canon of the show it wont be accepted by the archive.
I don't think it's deviation from canon that's concerning, just deviation from the show entirely. And even then, there's wide latitude in what subjects you can tackle. I remember a discussion once about whether to allow a story which was set in the comics universe & featured Superman and WonderWoman. I *think* they did allow it, though I wouldn't bet anything important on it, but it just goes to show you have to go to quite an extreme before they start judging by content.
There are somewhat tougher *rating* limits -- nothing over the American rating PG-13. But that's nothing to do with canon.
PJ
home today 'cause NC just had a whole *inch* of snow and therefore all the schools are closed