> What we really need is a switch from "first past the post" to approval/score/range voting, which would dissolve the two party system by eliminating spoilers and thereby making third parties viable.
Systems like approval voting or STV when used with single member districts do not reduce the two party duopoly. To achieve this you must use multi member districts, which has the effect of reducing the threshold to gain a seat. The best case study for this is maybe Australia, which has been running systems like this for a century. In their Senate they elect using very large multi member districts and have a representation from a number of parties, whereas in their House they use single member districts. And the result there is a two party duopoly.
For example at the moment in their Senate (multi member districts) currently there are seven parties and one independent:
Liberal (31)
Labor (26)
Greens (9)
National (5)
One Nation (2)
Centre Alliance (1)
Lambie Network (1)
Independent (1)
On the other hand the Australian House uses single member districts and third parties do much worse. For example look at how the Greens have a whopping 11% of the seats in the Senate above but an absurd 0.6% in the House below. This absurd 20x discrepancy for the Greens in proportion of seats between the Senate and House is the impact of whether you use multi member vs single member districts with RCV. And the size of the multi member districts will determine the size of the impact.
Labor (68)
Liberal (61)
National (15)
Liberal National (1)
Greens (1)
KAP (1)
Centre Alliance (1)
Independent (3)
As demonstrated here the Greens are clearly very popular with people but they just can't win in the duopoly reinforcing single-member districts. I would rather see us work to achieve an outcome like the the Australian Senate than the Australian House.
WRT your concern about who is your representative in the multi member case. It can be argued now ~40% of people who vote for the loser in our current system don’t have a representative, and a more proportional system would clearly improve this. So I think, if say we had RCV with five member districts, you could either just contact whichever member you prefer, contact them all, or they could introduce joint offices to work together, or a system could be set up to assign them to “sub district” that would be akin to our current districts. For example assign them based on who gets the most first preference votes in a district. Or rotate them every six months between sub districts. This might even reduce partisanship.