You know, it's funny, I was just thinking of something very similar to this lately. Mostly I was thinking that since the rights to the LotR & its appendices are the only ones available that to make yet another trilogy in epic scale it would probably be best to set it far back at the end of the second age and the beginning of the third. I would divide it myself into I - Numenor (about the downfall) II - The Last alliance and III) Disaster of the Gladen (this last perhaps expanding on adventures that the three survivors might have before coming again to Imladris). That way there could be a series of three trilogies, each about the one ring (in it's own way). The last trilogy could be used in turn to set the stage for a series on HBO/BBC chronicling the various wars/events of the third age. That could take a while but keep us all pre-occupied until they got up to the period of the Hobbit and tLorR again and could, this time, tell them as they should be told, in their proper mode w/out too many bells and whistles.
Just a wild thought.