Any 'class' system definitely would be debatable in this game for sure. Depending on rewards, players might be encouraged to dip down into lower classes and punish newer sparrers, which would be stupid.
As of now, the system allows the best of the best to participate, as there are no specific brackets. In the end, the best GST guild comes out on top. That's fine the way it is, because that's typically how regular brackets are.
If a class system were to be implemented, there would need to be more frequent events, because, unless there's a significant effect to losing and purposely dropping down for easy wins, a lot of people are going to take advantage of the newer sparrers eager to learn and soon meet fierce competition.
The problem is sparring is just not as popular as it used to be. Besides bragging rights, there's no reason to be a top tier sparrer anymore. GST has even died down a little, and there has been a surge in players competing simply for the regular GST shop like others have said.
I, personally, have always wanted to be a good sparrer. I never aspired to be the best, but I can at least hold my own against a very competent sparrer. My record is only slightly worse than a 2:1 ratio, but I was told I don't necessarily spar too bad.
But enough about me, my point is regular people, or kids, don't care about the spar community. Not even the admins give too many big poops about it besides GST.
Events like that would be cool. The ONLY one I see being a fantastic idea would be a Bug Catching event. Catching a big actually requires some movement and effort, not to mention you'll actually have to compete to catch bugs.
Loot collecting events would just come down to who can sit in the damn water longer, and nobody can control the loot spawning. Hardly a competition.
The Digging Holes Competition could be botted.
Some kid could find a cozy little corner in a cave and keenly control the entire competition via attrition, again, or a bot. (Ye like that? ;})
Then again, a lot of kids use this game as a social media site and just use it for communication and fashion. Nothing wrong with that, but it is annoying how they clog the server by going afk all day.