The Tory MPs are already saying that they will take drastic action if anyone gets the Tory leadership and tries to force through a no-deal Brexit. That means voting against them in a no-confidence vote, and they only need a handful to do that and the government falls.
You then get a general election with the Tories and Brexit party both standing for a no-deal, which should split the vote nicely. Labour will probably come out officially as a party of a second vote, and shore up their vote that way. Libs, Greens and Change UK will gather together a good set of votes, mainly from the centrist Tories that don't feel at home in their party anymore. But some from Labour as well, where people might not trust the message they put out (or it's still messy enough that they don't know what it is).
Chances are nobody gets a majority, and you end up with a coalition of centrist parties and Labour. They come together on the basis of a second vote, and hopefully a move away from FPTP at the same time. Remain wins the second vote, Farage and dribbles call it a traitorous act and start ranting and raving. Nobody cares. In 5 years time we wonder how we ever got ourselves in this mess.