I like the idea, but it really wouldn't be a new gamemode. All it would take is another selection board at the sg hub. And a few more arenas specialized for the smaller number of players.
Secondly, sg is not about kits. Kits are for KitsPvp. If you want bonus items to start, vote for tokens and spend them on coins!
Leaderboards: I think there doesn't need to be another leaderboard, since it really isn't a new gamemode.
Overall, I like it. I enjoy SG but am in late at night when there are only 3-4 people on SG. I think you could set it up so death-match occurs when there are two people left. If Zainos and some of the Mods and Admins like this, I will start building a map or two to provide a better representation of the idea.