If via some magic, the electoral system changed as I described despite those who won in the current system being in power, then the primary candidates would lose against moderate independents hardly anyone knew except for the reasons described. Except that the parties would forsee that and run different candidates using ranked voting in the primaries as well. Again, that is if somehow the changes could ever be made. Where it has happened it has often happened via referendum, and even then, it has been reversed on multiple occasions as well. I think Seattle just selected for local elections? It will be interesting to see how that goes.