Weirdly I think potentially the best chance in this election for electoral reform would be (as some polls are suggesting) for Labour to get about 40% of the vote but roughly 500 seats. I think this might just be a general wake-up call that FPTP risks (and actually) delivers perverse electoral outcomes. There could be a groundswell clamour for change were this to actually happen. And ultimately there will only be change if a winning party accepts that the system that allowed them to win is wrong - i.e. acting on principle rather than self-interest.
You mean, if the result is a blatant "travesty" of the popular vote. I think you may have a point. I do remember there was an election (2015?) where the SNP got about 50 seats and UKIP got about one but with a higher share of the vote.
I don't, by the way, think that the argument of "smaller party calling the shots" has any real merit. The Lib Dems had some influence between 2010 and 2015 but not the gun to the head sort of influence evoked by the argument (as witnessed by their failure to get any electoral reform). Also, the "coalition" between May's government and the DUP was not unduly influenced by the DUP, although, for the most part the Tories could manage without them.