About simplistic agreements: This is somewhat debatable, because at times some people's arguments really do sum up everything, and there's nothing left to add.
Nevertheless, simply "I agree" is not good enough. Even simplistic agreements must contain some explanation for the agreement, like: "I agree with points X, Y and Z made by A and the reasoning supporting them. Hence, I agree with the overall assessment made by A."
About necro-posting VS threads: Agree with Monarch, threads which have a definitive conclusion do not require any work, although users who necro-post can be politely discouraged from necro-ing needlessly. For threads which have an insufficient vote count, a necro post would be useful instead, and lastly, for threads which are invalidated due to change of statistics, the necro-posts will also be invalid.
All in all, I'm not seeing any reason to have a special provision for necro-posts.
About the 7-vote figure: The reason I had 7 as the minimum number of votes is because supporters of a franchise are often more active in their Verse's respective threads. It was quite misleading to have 4-5 votes (back before the rule was implemented), because any popular character managed to garner 3-4 votes very quickly, before any opposing arguments were made.
7 minimum votes on the other hand, is a sufficiently high number which prompts a somewhat balanced argument in equal favour of both Verse's fan-base. Of course, it's not a perfect number, but it was the reasonable figure I observed after going through a few hundred VS threads back when the rule was implemented.
Also, while I realize that not being able to proceed due to a lack of minimum votes is frustrating, it is easy enough to request others to partake in the thread and meet the minimum criteria. On the other hand, too less votes lead to biased results, as I explained above.
I don't see any reason to modify the current minimum requirement.
Conclusion: The only change necessary IMO is requiring members to not simply hand out simplistic agreements, but actually expand upon them sufficiently in order to provide insight as to which aspects of a previous argument they agree with, and also preferably explain why they agree with it.