I've been assuming the https://en.wikipedia.org/wiki/Reverse_Course is part of what gave Japan the heavy rural electoral weighting that's powered the LDP during nearly the entire postwar period. What do you all think?

I'm not sure. I really don't think LDP has lost. They're still the most popular party. Ishin and 国民民主(I don't know their English name) are basically the same neoconservertives as LDP. More liberal parties, CDP, communist party, or Reiwa are all unlikely to get majority support.

(BTW, you may be surprised, but Japan Communist Party has a small but solid supporters, and I'd say there's a good reason for that)

The most likely scenario for the next election is that LDP will regain the majority again, and nothing will change.