The advantage of the Silmarillion being written by Tolkien the way it has - is that it provides the Director (Andy Serkis?) to add as much to the 'historical' element as he likes. The Actors have free reign. The scenes can explore and more.
The Disadvantage is that although it is all written as if it was written by Homer centuries ago - it also leaves much vague connections, inconsistencies and a level of seriousness that goes beyond the LOTR, let alone the kiddy-silly Hobbit.
The Simarillion Saga would be 'very Adult' and might even be as dark and scary as the original ALIEN movie with a young Sigourney Weaver.
I think this is where Andy Serkis would do a better job than Peter Jackson, who is known for his mischievious and fun-pan inputs (like Carrot Man).

But hey, this is the Silmarillion - it would indeed be 'Serious' in many ways.
I reckon Morgoth for starters, would have to be x10 more scarier and evil than his little Elvish Prince Sauron. Afterall, Morgoth was a GOD.

I'm pretty sure that in the previous movies - there were many 'Fans' of the Battle scenes. But via the Silmarillion - I reckon Serkis will bring out a reality of such bloodshed (without the need for excessive gore) and its 'pain' (the total 'loss' and futility of it all), much like Spielberg managed with Saving Private Ryan and an Australian Director managed with his movie Gallipoli.

But via all that Darkness, there will be much Light and it will be far more brighter than Cate Blanchett's Galadriel. You would swear the Ancient Elves glowed in the Dark.