increasing curation rewards from 25% to 50% (yes, yes and yes! If we want more people to honestly curate then curation rewards should be as high as possible to disincentivize vote-selling and delegating to bidbots)

I think you bad economist. Sell your vote is much easy than live's curation.It's good if author's reward will be decreased on 33%? No idea how it can be compensated.

changing linear curve to convergent linear (terrible idea imo because a lot of minnows will be hurt because of this)

Every author will be hurted who don't buying votes.

creating a separate downvote pool -> basically gifting each user a couple of free downvotes per day (I hope this dreadful idea doesn't come to life because I have a feeling it's going to cause a shitstorm of unmeasurable proportions)

How to rule steem without good power flags? we can't control steem economy because we haven't effective mechanism. I won't flag spam because flagging don't give me any benefit but doing spammer angrier. Who need problems with current system as steem has?