To get back on track, I believe that if this board has ambitions to grow in size, the decisions about rules and debate will have to be taken early with a larger size in mind, aka with the hypothesis that the moderation will be much more busy and will not benefit from having the broad knowledge of all ongoing activity. This means looking a bit at forums such as SB or AH and trying to understand what they do and which works so as to inspire oneself with it. Some fast and loose rules will work with a small volume of users and content, but will be open to extremely effective rule-lawyering in a larger community.
Therefore, this question should not be considered with the current state of things in mind but with the desired one. If I may suggest something, it would be to avoid the pit trap of considering threads as isolated islands. For bad faith debating, one of the most enraging elements is when the culprit's actions are pretty obvious and blatant when taken as a whole but somewhat legitimate when taken within the singular thread.
The problem is that it can lead to complete ad hominem derails when the argument becomes accusations about the poster's general behaviour and shit-flinging using old quotes and such. What I would suggest is, to avoid this, to encourage users to make much complete reports, allowing explicitely to use, in the reports, previous posts of the reported user in other threads, to show a pattern of posting that would be bad faith. If the same behaviour was observed many times and was already ruled upon negatively or was repeatedly left hanging by the accused when called on their arguments, this would make for a much stronger case for what would be otherwise an acceptable argument.
So, possibly help posters with establishing report templates, a check-list of things to add to the report for smoother handling. And perhaps even, from the staff, establishing a precedent database for mod rulings on highly-contested subjects. Such a database, a list of links to the relevant posts with a very short description, could be left accessible to all so they can refer to it when the same argument gets thrown for the n-th time by a poster.
It would add a bit of work to the staff but would probably save a lot later when a larger community is established. In short, having a mix of Code Law and Common Law.