Would you have been happy with it as a 'replacement' though? Because that would have been what happened - we'd simply not have the existing Hobbit, it would merely be a curious collector's item for sale at high prices on eBay (as V1 is now).
Did you read The Hobbit first? I've got the feeling you did? This does have a point....
Would kids who read The Hobbit at an early age as a 'kids' book' still be caught up with the same enthusiasm for Tolkien if they read a darker book? Would they read it at all? It's one of those books that any parent, no matter how 'puritanical', would feel comfortable giving to a child to read, but I'm not sure they would feel the same about a darker story.
The thought of having the early chapters of LotR re-written fills me with abject horror though!
I've absolutely NO problem with the Hobbit 'not fitting' - I mean, nor does the Sil, and thinking along those lines leaves us with a 'canon' of one book, which is just stupid to my mind. Few if any writers produced a lifetime's body of work which was entirely consistent in tone, voice and style, and I have no problem that Tolkien's work is the same. It's interesting rather than annoying to me.