Upvoted because I respect the thought that went into this. I do think the reputation system needs some adjustments, not sure if these are the right ones, but the discussion should be opened.

One thing I would propose is cap the effect of a downvote on anyone with significant positive rep to only push the rep down to exactly zero, regardless of the SP of the downvote (not deep negative from one downvote). It would then take another downvote to push it negative.