In OTL, the Lib Dem decapitation strategy failed massively, with many of those targeted increasing their majority. How could it have succeeded and what would have happened to the Tories had it succeeded?
You probably can't get it to work, it failed too badly.
However, as for the impact, ConservativeHome lists four of the targets: Theresa May, Oliver Letwin, David Davis, and Michael Howard. That's the force behind Cameron's Home Office and a future PM, a guy who was part of plotting Cameroon era policy and the coalition, and an MP that was famous for civil liberties in the 2000s and later was a big figure in Brexit policy. Any of these three knocked out is a big deal.
And taking out Howard would be the biggest of all if you can do it. That means the Tory leader has lost his seat as well as the election, that the Liberal Democrats have landed a major symbolic blow (because they're still a smaller party) on a party out in the wilderness. That's bloody great if you're Kennedy and the Lib Dems, terrible if you're the Tories and trying to figure out how to return to power. It looks like you're failing and they're the future. Unfortunately, this sort of victory likely has a downside of Kennedy sticking around as leader despite his alcoholism affecting his ability so it may damage the party in the longer run (and wouldn't be good for him).
Howard: Not a chance.
May: Maaaaybe if it became a truly gargantuan wave election, but otherwise-no.
Davis: Similar to May.
Letwin: Small victory margin and they'd also come close in 2001 and 1997. If the time is right they could do it.
