I wish we could do something like the Jungle primaries that some states have where all the parties run together and the top candidates advance to the general election regardless of party. That seems to put a damper on extremism.
Ideally though, I'd like to see us move away from the presidential system to a proportional parliamentary system, but that would take a constitutional amendment.
It's quite an uphill battle because the economy is complex and Trump gives people simple answers (that won't actually work).