I guess my reading comprehension takes a hit as the hour gets later, but if it means a forced death for the protagonist, then I can't really go along with it. No doubt the replay value of the game would drop to zero, and as one who weighs the worth of a game by how many times I can play it, that would be a pretty bad thing. I typically butt against forced PC deaths in a game like this, because it kind of makes the whole journey seem like a massive waste of time unless there's something meaningful that can be added to it, but I set the bar extremely high for this, because forced death is just a bitter pill with little value in and of itself.
I guess I don't 'immerse' as much as a lot of players do, but I actually don't have much investment one way or the other in whether or not Shepard lives or dies, as long as either living or dying has some kind of storytelling significance. Way back when, I had an idea as to how Shepard's auto-death could have been done in a somewhat more interesting way: For instance, maybe you could play up the idea that after Lazarus, Shepard is somehow on 'borrowed time' (something like Captain Sheridan after Z'ha'dum in Babylon 5, for anyone who's seen that show). Perhaps the Lazarus implants are breaking down. Shepard's dreams could then be explained as a side-effect of this, so that their function of foreshadowing Shepard's eventual fate makes more sense, story-wise.
With this scenario, you'd have more of a story justification for forcing Shepard's death that ties in with an already existing plot development, a way to add thematic heft to Lazarus, and an explanation of why the Lazarus project doesn't actually constitute a Khan's blood-style cure for death. I know no one's going to like this idea, because it involves Shepard dying no matter what; I'm just saying that if you had to make the death of Shepard an inevitability, this would have been a more interesting way to handle it IMO.
RE: The OP's question.
I don't know if the existing ending minus the Catalyst would constitute a good ending per se (too abrupt, perhaps?), but I think it would definitely be preferable to what we got. Maybe I'm just more used to stories where key mysteries are left unsolved, but I didn't really need much of an explanation of the harvest (something like simple self-interest would have sufficed for me). In fact, I was dreading it: The harvest is just kinda dumb if you think about it: What rational justification could there be for wanting to kill all intelligent life on a 50,000 year basis?
It was plainly obvious to me from the beginning that the basic setup of the harvest wasn't constructed with some great scifi concept in mind but more as a way to move the story along: The Reapers wait 50,000 years because otherwise the setting wouldn't be possible, they want to destroy all organic life because that gives Shepard a reason to oppose them no matter how sociopathic he/she is, etc. Within these constraints, I was extremely pessimistic that you could construct an interesting after-the-fact rationalization for why the harvest actually kinda-sorta makes sense, and the whole Catalyst sequence confirmed all of those fears for me.