At the first look, it seems a great idea (I think I had or agreed a pretty similar idea sometime in the past too, but I won't search now for that topic).
Unfortunately, at a second look, it's no longer that good imho, since this ignores the fact that some smart and worthy people may have a life outside the forum and will punish them for that. Or it ignores the fact that forum users did and will pass away and it will look ugly/strange to see this or that user has became newbie again, somehow ignoring his achievements.