I disagree that downvotes are the answer to the problem you raise.

With downvotes in the current system a whale could upvote the return, upvote the ones they like, and downvote all other proposals. Then the barrier to entry for a new proposal would be FAR FAR worse than it currently is.

You can't just slap on downvotes and say "yep everything will be fixed now". You will have the same issues, only exaggerated.