The point of SODA isn’t so much as a serious proposal; I prefer 3-2-1 for that, mostly because it’s easier to explain. SODA’s advantage is that, under “reasonable” domain restrictions, it is completely strategy-free. (Using my admittedly-idiosyncratic definition of “reasonable”, it’s actually the only system I know of that is. It’s a non-trivial proof, so I don’t expect that there are other proposals that I’m unaware of that do this.) Forcing candidates to pre-commit to a preference order is a key part of proving that property.
I do see the point of your proposal of having post-election negotiations — it gives real proportional power to even losing blocs of voters, and unifies that power in a way that helps favor cooperative equilibria. Some of that same kind of thinking is incorporated into PLACE voting, though in that method the negotiations still happen pre-election. Even if post-election negotiations are a good idea, I’m skeptical that a majority of voters would want a system that “forced” them to trust somebody that much, so I think keeping it as a pre-election process helps make a proposal more viable.
The point of SODA isn’t so much as a serious proposal; I prefer 3-2-1 for that, mostly because it’s easier to explain. SODA’s advantage is that, under “reasonable” domain restrictions, it is completely strategy-free. (Using my admittedly-idiosyncratic definition of “reasonable”, it’s actually the only system I know of that is. It’s a non-trivial proof, so I don’t expect that there are other proposals that I’m unaware of that do this.) Forcing candidates to pre-commit to a preference order is a key part of proving that property.
I do see the point of your proposal of having post-election negotiations — it gives real proportional power to even losing blocs of voters, and unifies that power in a way that helps favor cooperative equilibria. Some of that same kind of thinking is incorporated into PLACE voting, though in that method the negotiations still happen pre-election. Even if post-election negotiations are a good idea, I’m skeptical that a majority of voters would want a system that “forced” them to trust somebody that much, so I think keeping it as a pre-election process helps make a proposal more viable.