If you have opening statements limited to a paragraph per person, this would limit the amount people could say, force people to be more precise, and make it harder in general. Anything over a paragraph would be deducted from the final score percentage.
The actual exchange in debate would operate under the same rules, say a paragraph or so. The rules to be determined, though common debate procedure seems best. Say, if one argument requires more than a paragraph of explanation, a person can ask to deliver further testimony. It is the choice of the opponent to allow it or deny it. Debate formality is also a wise thing to uphold as well. Also, a time limit is a MUST.
It would also be wise to limit the number of arguments for a position, as an argument could go on for a long time. More arguments given than the limit would necessitate a percentage deduction from the overall score or disqualification.
The overall score should consist of two polls. I'm sure these widgets are easy to construct. One poll would be for regular members and another for administrators (the administrators (or appointed judges) weighed 70% and than the regular members at 30%)
What I have experienced in debates that is most problematic is that the rules are unwritten. There has to be a constructed document stating what the rules are and provisions for each instance with the approval of the administrators that can be cited and clearly read to legitimately overrule or protect ones interest. (As a side note, I'd be more than glad to formulate a debaters bill of rights if the need be.)