I do this all the time, I always write everything down but my works usually involve rewritten the current series and always start post R.
I did toy with the idea of Rewriting the series completely including Sailor Sol from Jendra's Universal (simply because I love him which is why he is in almost all my fanfictions) but I always hit a dead point.
Pusaku-sans Masterpiece might have given me the final push* - story-wise, as K. T. did with his Drawings - in the right direction to come out of my shell and I hope that the current stuff will turn out better than my first attempt here which (luckily?) went into Oblivion along with the H-Section of the forum as that one just would've been too risqué and ecchi for sensitive Readers.
*Although (s)he's been faster with some of the best jokes/gags, like
"Ami pulled her book even closer to her face, let herself sink some deeper into the bathwater and resisted the urge to repeatedly bash her head into something hard..."
P. S.: As I was working on the Series' Family Tree, I was wondering: If you were on the receiving end of a one-sided crush, what would make you that in terms of Relationship? What would be the correct word to describe, "Love Interestee", or what?
I don’t think I have ever discarded an idea, be it fanfic or original story. It’s however possible that I might have had an idea or two that I didn’t think much about at the time and since then completely forgotten about....
I still have that fanfic idea of the Sailor Moon and Mermaid Melody, I'm stuck on the process of how to write it. There's so many iterations of Sailor Moon, I'm taking what I like from ech one. The fanfic is a MMPPP inspired AU, in case anyone's wondering. I might have a case of the dreaded "writer's block". So no, I haven't discarded my fanfic idea.
"Tuxedo Mask fanboy from the future discovers he is destined to become a villain and snaps. Thus, Reverse Endymion is born." I later realized it had already been done before and I was just rehashing Reverse Flash's origin story.