Welcome, Herenya! It's always good to see new people here, and have new ideas and interests!
I second what Inzil said. This thread seems long-abandoned, and many of us here haven't even seen it before. You could post your proposal here, though it's not a perfect fit, or you could make a new thread for it.
Although we have a newly-made fanfic forum, I think it is quite literally still "under construction" and there are some limitations about posting there. However, you could try the Mirth forum if your story is more of a light entertainment or comedy, or Novices and Newcomers (a forum where various odds and ends tend to get shoved if they don't fit elsewhere) or even Books if it is more serious or more scholarly.
But again, welcome to the Downs, take a cup of your beverage of choice, kick back, and enjoy! Go wherever your fancy takes you. It is much like Rivendell in that everyone is free to wander where they like and take part in all that they enjoy about Tolkien - and there are always more unexplored threads and corners, if you have the time to explore them.