Then you push the coalitions forming outside of the party process to parliament where voters have no say compared to forming coalitions to within the party where party members have a say.

Err .. Maybe?

The big coalition in Australian politics, the LNP, has been integrated enough (in most states) to share a platform and field single candidates, giving people that choice ahead of time. We haven’t had a post-election coalition formed in some time.

But I think you might be thinking more of PR systems rather than preferential votes. In Preferential systems you still have a single winner of a given constituency, but the method of choosing that winner is more focused on a wide basis of support rather than on just who has the most votes.

I.E. if you have three parties for a seat, Centre-right gets 40% of the vote, Centre-left gets 35, “Legalise Everything Dudes!” get 25.

Under FPTP Centre-right takes it.

In a preference vote, we discard LED and count its voters’ second preference. Let’s say the split is 4:1 left/right. This leads us to Centre Right getting 45%, Centre left on 55% and the seat goes left. In this case we end up with a candidate acceptable to a larger part of the electorate. And the existence of LED didn’t split any votes, you can’t say a vote for a smaller party is wasted in this system, or blame smaller-party voters for Right getting in rather than left.

Under PR you’d split the seats in the parliament by national vote share (as in the Australian Senate)