I don't think it's deviation from canon that's concerning, just deviation from the show entirely.
Yes but what is the show in terms of fanfic? I’d say a number of canonical elements, ignore or twist enough of them and sooner or later depending on the reader, he/she wont consider it L&C fanfic anymore.
If someone writes a story about Harry Potter, reuses the plot element of the L&C pilot and wan’ts call it a L&C fanfic, it’s no skin of my nose, but I assume that that such a expression of creativity would be a hard sale to the archive administration.
