There are plenty of anime that have a lot of filler, such as Naruto or Bleach. However, there are a lot of filler episodes that fit completely in the storyline, and could easily have happened. Wouldn't it make sense for the mangaka to declare some of these as canon?
This would clearly satisfy the audience as it kills a lot of people to see good content that didn't really happen. But building on this, would it be plausible for the mangaka to create a new category of episodes in between filler and canon that simply labels episodes as correct so people can watch them, but skip over them since they don't contribute to the plot? This would seem like a step up since there is a clear distinction between outrageously impossible filler and filler that could actually have occurred.