It would be appropriate if they only accept accounts with less negative ratings than positive ratings. Neutral would also be allowed of course. That would come closest to the rules we had before the update.
This would be an interesting metric to see used. I think it would still be to rigid though as it still gives a single Dt user out of hundreds the ability to taint an account for what they believe to be a good reason. Then the user would have an uphill battle to get someone to counter it, if they have no history with any other DT. Just a possible issue.
That's somehow true and maybe a mixture out of this suggestion and the one from yahoo62278 would be better, especially with an increasing number of random users in DT. After all, the previous red trust was still much harsher, where a single DT user could ruin accounts and 2 positive ratings were needed to encounter one negative to turn the account into neutral again.
A good bounty manager will review the accounts anyway and if the reason for the tag is not justified the account might get accepted. Like you said, the mdayonliner issue could be an example where a reconsideration makes sense, he's currently at +2 / =3 / -3