You just need two-party preferred voting so that you can vote first for a niche representative if you wish and preference a major party. In Australia, for example, it allows parties outside the two majors to have some influence, which I think is healthy.

While that is often the case, it is not necessarily the case. Look at France for a counter-example.

The downside is that the French "solution" was/is for the parties to enter into extensive election alliances to prevent splitting their potential voters, so it's an ugly workaround for a broken system, and you still get horrible distortions but it still better represents the actual views of the electorate.

Time for a proportional representation clause.