1) The bw levels for user classes are outdated when seedboxes are used so often. A TB is the highest class on most sites and that takes less than a month if you really want it. And if you are stuck with under 100kb/s upload, get with it.
2) The privileges are nothing special. OMGZ an NFO file! Maybe a forum!
3) 15/18/20 weeks? Ok that's not really even that long a time commitment. Why not go by months or years to distinguish real users of the site?
Maybe it should be either time or upload/ratio. Otherwise the whole thing just doesn't really make sense for either seedbox users or slow speed home users.
But actually I think there should be no classes, because there is no real extra benefit for using the site. Check the top 10 uploaders on many sites and most of them have under 10 comments and forum posts. What are they contributing to the site really? A Gbit connection is all.