I'd like to see a New Standard Edition of the Silmarillion, and contribute. But what kind of edition can be made? CRT wanted to publish a Complete Edition, and fill up his father's original design: to present the whole Elven legendarium, from the Creation myth to The Rings of Power ("the last Tale"), with completed texts. He could but fail in this since QS, the core of the book, is unfinished, and CRT admitted he had to contribute himself to fill in the blanks at one point (The Ruin of Doriath); and the elvishness of the Corpus as written/published is most questionable.

CRT himself pointed out in HoME1 the problem which should have been dealt with first: who wrote the Silmarillion? In other terms: whose vision is it?
Since he chose to publish works as most finished as possible, the texts he had to resort to weren't the most updated ones. They are indeed said to be Elvish, and from the best source (told in Eressëa to the mariner Ælfwine). The snag is that they feature a flat Earth and the old Sun-Moon myth.
The old cosmology was a hard-lived conception in Tolkien's legendarium, and though he saw it a big flaw, he was reluctant to wipe it away ("a pity really, but it is too integral to change it", draft to Letter 115, HoME10:5). However, he eventually adopted the new cosmology and held to it, as is seen in his later works. It even appears in a published book; LotR carefully avoids any reference to it, but a significant change was made to the 1966 edition of the Hobbit, in the passage about the Wood-elves (end of Ch. VIII):

While the Vanyar and Noldor and Teleri "went to Faerie in the West", where they "lived for ages", the Wood-elves "lingered in the twilight of our Sun and Moon". The former reading was "twilight before the raising of the Sun and Moon".

It may be argued that the passage doesn't make clear that "the twilight of our Sun and Moon" takes place *before* the return of the Noldor, but the correction in itself shows that Tolkien preferred the unambiguous allusion to the "old cosmology" to be made meaningless.

In late writings, Tolkien didn't reject the "heretical" conceptions; he ascribed them to Men (and the Grey-elves). This was stated in the clearest way in the Shibboleth of Fëanor, for instance, where 'The Silmarillion' is said to be a Númenórean or 'Mannish' work. As for the true Elvish tales, they had to be written anew, which Tolkien almost never did. So Ælfwine's intervention, which since the beginning, had framed the whole legendarium, was necessarily erased.

Fortunately, the new Númenórean conception made it easy for the editor of the Silmarillion to link it to the Hobbitish tradition of texts, set out in LotR, Note on Shire Records; Tolkien, when preparing the 1966 edition of LotR, had thought of transferring the "Note" to the Silm. But his son didn't follow him on this path: when we're reading the Silmarillion as published, we're left to imagine, from internal evidence, that it is a genuine Elvish work, since no clear statement (such as an "editor's note") leads us to think otherwise.

A 'Revised Edition' should make clear that "what we have in the Silmarillion etc. are traditions... handed on by Men in Númenor and later in Middle-earth (Arnor and Gondor)... blended and confused with their own Mannish myths and cosmic ideas" (HoME10:370). This would be IMHO truer to T's expressed intent and allow us to explain easily the "errors" carried on in the Ælfwine-tradition. As for the mariner, it seems to me that he has no place left in a Númenórean-Hobbitish tradition, but to eschew his name from the existing texts is still an uneasy matter.
This 'Silmarillion' would have to be unfinished, since the gaps in the narrative (most of them at the end of QS) can hardly be filled. After all, these manuscripts have been handed on for thousands of years... Here the editor should step forward, and give extracts from earlier texts or later outlines (as in Unfinished Tales) with reference to HoME. No lengthy commentary, but carefully documented quotations . Thus readers who love accuracy know where to go for more, whereas the others can enjoy the story and know how it ends, even in a condensed way...

Philippe