There is no single "accident" that can turn the tide of a war *if it's being played from both sides*. The decks are stacked. The game is thoroughly rigged. Any "accidental" gains can be artificially hampered. The house always wins.
The closest they ever came (that we know of) was the incident with Tup and Fives.
So I say "What if something unexpected happens?"
And your reply, twice, is that "Nothing unexpected could happen."
Truly? "How can you expect the unexpected?"
When Dooku kidnapped Palpatine just before Revenge of the Sith, Palpatine should have been disempowered as the authoritative head of the Republican Senate. For an hour or two Palpatine's Deputy was acting Supreme Chancellor while a Separatist fleet was above Coruscant leveling cities, and murdering hundreds of millions of citizens... Or they all suck at their jobs.
The acting Supreme Councillor would have been considering surrender as the deathtoll mounted, especially if they did not know that Sheev controlled both sides of the war.
Did the Jedi know about Order 65?
It's from a novel printed in 2007, which means that it was canon until Disney bought Star Wars.