Although I agree that some questions seem to be closed overzealously, I don't see the need for all the extra debate. Do you really want to spend all that time arguing over the detailed merits of questions? Coming to a consensus sounds like the ultimate committee nightmare. A simple vote makes your opinion known concisely and with the minimum of fuss. If the majority of the community agrees, your opinion will stand.
The one simple change that I think would dramatically improve the open/close system is having a vote not to close option, rather than waiting to reopen, to avoid the close-reopen asymmetry. See that link for the detailed discussion.
You are also suggesting providing much more power to lower rep users, which I think is a completely separate point. In my opinion though, the ability thresholds are there for a reason, and work pretty well, for the most part.