Interesting stuff.
A few extra points, it is a while since I read the History of the Lord of the Rings volumes but I am fairly sure that Tolkien never intended to kill Frodo and Sam because I am sure CT quoted a note that JRRT had made saying if one of the hobbits died it should be the 'cowardly Pippin' ( I think this was before Faramir arrived in the story giving Pippin scope to redeem himself).
While it does seem on the surface that a disproportionate number of major characters die (and stay dead) I think it would be hard to pinpoint any major characters whose death would have made the story 'stronger'. I seem to remember that Eowyn was originally doomed (Faramir saving the day again
). I was about 11 when I first read the book and I am sure that I would have found that unbearable.
The fact that it started as a children's book may have been a factor. Although I wouldn't say that Tolkien is particularly soft hearted on the youngstock - I think it likely that The Hobbit was the first book I read where major characters died and though I find the Hobbit's style annoying often, the death of Thorin and the summary dispatch of Fili and Kili, I still find as moving as I did when I was nine - possibly more so since at nine I was probably more upset by the goblins eating the ponies
. I wonder if it is significant that apart form the Nazgul's steeds, only poor old Snowmane bites the dust in LOTR .....
For me the fate of the characters is a reflection of the major themes of the book, renewal, the triumph of hope over despair, and fellowship over self aggrandisement. The only major characters who I feel could have been killed off without compromising these to a greater or lesser extent are Legolas and Gimli (though I am fond of them both) but since they function as little more than witnesses for their declining peoples once Aragorn has taken up his military role in Rohan, I don't see that slaying them would have any useful purpose.
The healing and symbolic rebirth of Eowyn and Faramir have significance in that Faramir the steward, knows and recognises the true king, ensuring the restoration of the correct order of things (and following the model set by his kinsman, Prince Imrahil, who personally does not hesitate in acknowledging Aragorn, and who is the heir of a house who surely would have had enough of the bllod royal to make a claim to the throne but instead remained loyal to the possible return of the king).
Tolkien is also clever about making you care about minor character with a great economy of words. I know fromanother thread that I was not alone in grieving for Halbarad though he has only a couple of lines. The funeral laments are also effective.
Although, I know it is possible to read and love the book without knowing or noticing, or indeed caring, knowing about Tolkien's Catholicism, (though I know there are much better theologians than me around, I think it is fair to say that this is a more specifically Catholic concept), I do suspect that he was keen to allow his characters to make a 'good death' . Boromir and Theoden get their chance to make their peace, Boromir's final speech with Aragorn could be read as confession and absolution - although as an echo rather than an absolute representation - I don't see the LOTR as that directly allegorical (but that discussion goes on elsewhere!). Denethor rejects the chance to make a good death leading his people on the battlefield and his suicide is seen as heathen - a direct contrast to Aragorn giving up his life, surely only a few yards from the site of Denethor's pyre, which is seen as a righteous act - not fighting 'the gift of the one to men'. Although Boromir quotes Tolkien saying that Frodo's claiming of the ring was not a moral failure, and personally I think that Frodo died at Weathertop in the sense that he lost any possibility of returning to a normal life and had 'crossed to the other side' - think of Gandalf's impression of him in Many Meetings (cf CBC ), to kill Frodo at Mount Doom would have robbed him the chance of making a truly 'good death', reconciled to his life and death. Sam has to survive in order to be and do all the things that Frodo has sacrificed.
Good does triumph over evil but it pays the price. Maybe not in blood but in change Not even the remote Shire survives unchanged - although I rather like the fact that after the restitution of the monarchy in Gondor , meritocracy asserts itself in the four farthings and the gardener's son rises to equal the hereditary powers. Change is not always progress but neither is it always decay.
Another factor to bear in mind is that I think it may be a realtively modern phenomenon to perceive not killing off your heroes as a weakness. Louis de Bernieres was criticised for his ending to
Captain Corelli's Mandolin - personally I am glad he found a third way between an 'unrealistic' happy ending and an unutterably bleak and hopeless one and I think Tolkien does the same. I don't think that The Grey Havens could be more effective and affecting if someone physically died. As with Aragorn giving up his life it is the fact that there is a choice, superficially tempting but wrong, that adds piquancy.