Calvin, your idea has some real merit and like JavaJones says, part of the plan for the new review system is to break up the components so that some people may concentrate on filling in details and comments for one program, and some for another.
I like your idea of harnessing the fact that people naturally tend to champion one program or another, and the idea of having people who liason with the software authors; authors will also probably frequently want to be responsible for (and best informed for) talking about their own software.
The main puzzle that needs to be solved with this is to keep authors and others from saying their program is the best all the time and not giving an objective appraisal of strengths and weaknesses.
What I was thinking is that, while a main reviewer (or two) would be respoonsible for comparing and giving opinion on various performance of the apps, we could use people as you say to offer counter-opinions, rebuttal, and fill in details, feature matrices, etc.
In other words, I think we still need an objective reviewer(s) who can compare programs and critique them, and provide some consistency to the reviews, we could really benefit from a focused advocacy thing as you say to get more people involved in helping to write descriptions, elaborate feature matrices, and just in general make sure that each program is fairly treated and explain stuff and make sure the reviewer doesnt miss anything or get anything wrong.