I think, whenever possible, Steem problems should be solved inside the Steem ecosystem.
Agreed!
Downvoting... it’s tricky and will likely be abused. While, if used correctly (with the parameters you mentioned), it could be healthy for the ecosystem, the harm caused by undeserved upvotes will be insignificant compared to the damage caused by abusive downvotes.
Some people express their opinions in a toxic manner. Even if we exclude the major stakeholders or 'big whales' and the manipulation they may engage in with their downvotes, the level of toxicity some individuals can exert through their downvotes can still be overwhelming. I'm talking about emotional damage here.
I agree with this. I'm pretty sure that many people were driven away from the ecosystem by the overly aggressive "downvote wars" of the past. I definitely don't want to see the capability used that way again.
I also noticed recently that there are apparently now services providing "downvote insurance", which complicates the problem even more.