Octo, there are inherent flaws in any system we'd adopt, and in the current system. There isn't much way to get around them without being entirely too complex and objective towards certain players/times/achievements, hence my suggestion earlier.
I think it would be possible to break down the system I explained a bit more, though the game doesn't really give a very good method of that. If you use the obvious division of A/SA/00A, you'll encounter problems on levels where things are mostly the same (think of Statue, Facility SA/00, Streets SA/00, etc).
Above all, I think if any major change is made to the REAL rankings (not any side rankings that you guys can make yourselves and host on SRW), we need to keep in mind that new players DO still appear at this place. The extensive growth and appeal of The Elite is in its' simplicity. You, of all people, should know how tough it is as a new player to adapt to the incredibly complicated Kart rankings systems, which is something we need to avoid here. New players can and will highly impact the future of the ranks, as has been seen over the past 2 or 3 years.