I don't think you understand how it works... An upload:download ratio must average (not simple mean, but that's because ratios are nonlinear - I can't recall the mean type but it's the nth root of multiplying them all together) 1 in a system where all uploads and downloads are logged in the same tracker. It doesn't matter who the uploader or downloader is or how recently they made their account. That's what I meant by a closed system.

An open system would be where you download parts or all of a given torrent via another tracker, and the same with upload. The private tracker only logs what you downloaded and uploaded though it, so your ratio from the perspective of that tracker is different to in reality.

Even if you ignore the first 5 files or 15GB or whatever for new users, if you have those files then great but do you really want to turn it into a betting game of seeding supply and leeching demand?