I'm supporting a 50/50 split

Exponential curve is likely too strong because n^2 means someone who has 100 times more SP than you has a vote that carries 10,000 more weight than you. Now that people are more sophisticated, this perhaps would open up to even more abuse than the current system

But indeed some level of superliniearity is necessary. I like the convergent linear curve proposed by vandeberg as far back as 3 years ago. It has a superlinear head that forces all profitable spam into the light, and a linear tail so no collusive piling on between whales/bid bots

I also think a moderate amount of free downvotes are necessary. Basically every measure helps, but every measure has their own downsides if you tune them up too much. This is mostly an optimization problem.

I broadly agree with your points and think it's better late than never. I share your frustration as I've been proposing this for over a year, and I'm grateful that recently @justinw, @andrarchy @vandeberg and other inc members became receptive to these ideas