Besides the blatantly obvious flaw in this story - that hand-written manuscripts can be easily altered by "evil men", and are not detectable to anyone who has normal working eyes, God, who foresaw this event, came up with a divine solution for Nephi to record the history twice - once when transcribing the Book of Lehi (from the Large plates) and again when transcribing his own record - the Small Plates of Nephi:
So all up, including the abridging, the same events were written FOUR times on metal plates: once by Lehi, twice by Nephi and once by Mormon - that's a LOT of effort! Is this a likely plan, given that space in the golden plates would have been a premium? Keep also in mind how hard it must have been to produce the actual plates and then write multiple copies.
Think about it rationally. Does it really make sense, that God's divine solution to someone losing the translation was to include the same story twice (in the plates found by JS), but in different words? That would be like me giving my kid $20 and knowing he was going to lose it, my best solution is to have another $20 on hand. Really? Or, would I take extra measures, knowing he was going to lose it, to ensure the first $20 was not lost?
Well, if I were God I would have foreseen these events, and stuck with my "No" answer. After all, I am the all knowing God - I know what the "Yes" response would result in. No one bullies me into a change of divine answer! (A point has been raised that the God that changes His mind after being nagged doesn't sound like the God described everywhere else).
Of course if you are thinking, "But what if God wanted to teach the impertinent JS a lesson?" Well again, if I were God, I would do this without risking losing the translation. I'd have commanded him to make a extra "backup" copy of his 116 pages of manuscript. Yes, it would have slowed down the work, but not to the extent of time JS lost his translation privileges. And had the conspiring minds of evil men altered the original words, their crazy nonsensical plan would have been thwarted!
[UPDATE: And of course, being all knowing, why couldn't God just tell JS where the missing pages went?? Or even better, make them miraculously appear - (without grammatical errors and typos)!!!]
No, no, no! God thought it best that making poor old Nephi rewrite the same history on multiple metal plates was easier than a 19th century scribe making an extra copy on paper. Really?
But wait! Having said all the above, keep in mind that JS never actually "translated" anything. The entire text of the BoM was produced via "revelation", and did not even require having the Golden Plates present - more times than not, the golden plates were either covered up in the corner, or sometimes, not even in the same room!
As someone else aptly put:
"So put the lame 116-page explanation together with the nonsensical translation of plates without the presence of plates and we have...God going to extraordinary lengths to have SECOND set of plates made so that they could NOT be used, in place of the first set of plates that were not used."
Conclusion: Which is more likely, God caving in to pressure and enacting a crazy 1500 year plan with an nonsensical solution that explains nothing and results in a lot of extra effort by Lehi, Nephi, Mormon and JS...OR...(wait for it)...JS simply made it all up?!!
References:
MormonThink - The Lost 116 Pages of the Book of Mormon
MormonLeaks - Necessity is the Mother of
The Stolen Manuscript: The lost 116 Pages of the Book of Mormon (Excerpt from The Golden Bible
(and just for amusement) South Park's rational take on it.