I'm not sure if this is very easy to do on the blockchain level. We are hoping to get separately delegatable downvotes which would partially address two primary conerns:
Fear of retaliation of downvotes - If you're a step removed and the downvote bot also has 100 other delegators, you're far less likely to face retaliatory measures.
Whale apathy - We want relatively inactive whales to delegate their SP and help clean this place up in a way that won't interfere with their curation delegations.
Also, if downvotes are handled by a relatively impartial or even anonymous third party, it'll likely be more proportion and precise rather than emotional and potentially unfair.
Yeah, functionally it would be a difficult thing to achieve but the measures you state above would definitely work. Especially number 1. I would be game for that