Condensing the amount of people in the Power Rankings would only discourage the community from growing. One of the biggest motivations for new people to attend tournies is to get onto that list, but making it so they have to become Top 5 material in order to get recognized would probably turn some people away, because to them it seems like a highly unrealistic endeavor. And seeing that two or three people in the top 5 will always be there, having PR limited to five people is not exactly gonna be an exciting list to keep an eye on.
I definitely agree with Tommy in that the PR should be updated more frequently, as it would make the community feel more active, even if it really isn't. Also, the re-inception of Challengers Approaching would be nice, as it gives the people who aren't as good something realistic to work toward.