I agree, while one often might think they have a great idea on their hands when they start writing they realize that maybe the idea wasn't so great.
For years I've had an idea for a fanfic rolling around my head. I've got probably 15 pages of notes on it (I named ships, fighter compliments, commanders, jump routes, character sketches, plot line, etc) but have never gotten around to actually putting it down.
The idea was a quasi-deep raid on a Kilrathi forward refit base in the Daghk System in the 2640's with a bit more emphasis on a fleet action type of engagement instead of just fighter strikes. Maybe one day I'll get around to putting all the information I created to good use.
But best of luck to you.