Your last part, about removing downvoting completely, coupled with my weighted scoring system, is probably the best solution.

I know you have concerns about ‘jerkvoting’, but that’s going to be a potential risk in any situation where players have input into the system.

What I would prefer overall is a system where the top 5% (or less) of submissions are reviewed by CZ (or even a group of veteran players that they personally select), and from those ‘Finalists’, they choose which one to add into the game. Any of these ‘Judges’ that have a submission in the Final Round would have to recuse him/herself from the final process for that particular round, to keep it fair.

In other words, it’s our job as the player-base to filter out the majority of the drek, and submit to them a handful of choices to pick from. Automatically adding content just because it got the most votes is a bad system, IMO.