The Steem EIP

Yes, that's the one (facepalm)

As repeated numerous times, call it "Steemit EIP" if anything. Using a naming that's not leaving room for any other proposal name is a scummy move. We already know you have full control over this blockchain's governance, no need to rub it in.

While it does not incentivize curating through downvotes,

Yes it does, curation via downvote is more likely to increase the value of the token and therefore using an amount free downvotes bring a net positive monetary value to the user.

If everyone did this, then no content would have any reward shares and would then not get any reward.

What kind of FUD is this? You know full well this would never happen. We have a hard time having any downvote how can you think the sum of all users actions across all content would be more downvotes than upvotes. There is no word for how ridiculous that is.

I think your hybrid solution is similar to this one can you confirm? https://steemit.com/steem/@transisto/separate-downvoting-power-pool-concept-visualized

Allocating rewards to the right initiatives is more important than content discovery.

Why have an arbitrarily over-sized upvoting pool compared to downvoting? Why so much complexity?

Reddit statistics shows there are 10 times more upvotes than downvotes (without monetary incentive). People will invariably downvote less even with 100% DV pool because here votes have economic value which has more direct real life consequences. If we want to have a balanced ecosystem some community member/stakeholders will have to take the responsibility to downvotes for all of those who don't. They will be called tyrants and be at risk to become target for off-chain/real life attacks not just benign downvote retaliations.

Steem will also need way more downvotes to counter collusion of for profit voting guilds if a switch is made to 50% curation reward.

As part of a "deep dive" I would review the change in number of downvotes that were caused by Steemit recent changes from flag to down arrow.

You forgot to mention that many witness suggested that the reward pool be independently delegatable. I didn't think this was all that important with 100% downvote but it for sure is if only 25%.

Ps: I upvoted your post because I think it's an important discussion to have but I find your analysis to be very shallow and possibly disingenuous.