I just came up with a great idea. So the jewels are scattered. My idea is that Jet the Hawk and Sora each recover one. Jet invites people to a tournament with the emerald as the prize. The winner will face Jet for the emerald. Sora's would revolve around kingdom hearts.
The Jet tournament would look like this
Sonic vs. Captain Falcon , Mario vs. Knuckles, Amy vs. Ryu (SF), Tails vs. Bowser, Rouge vs. Peach, Luigi vs. Link, Shadow vs. Ulala, Dr.Eggman vs. Nights, Zelda vs. Chun-Li (SF), Reala vs. Fox, Daisy vs. Pit, Wario vs. Lucario, Waluigi vs. Blaze, King Boo vs. Omega (gamma), Captain Commando vs. Ken (SF), and Kirby vs. Silver.
Then round 2.....
Sonic vs. Fox, Knuckles vs. Pit, Ryu (SF) vs. Wario, Tails vs. King Boo, Rouge vs. Zelda, Link vs. Blaze, Shadow vs. Ken (SF), Dr.Eggman vs. Silver,
Then round 3....
Sonic vs. Ryu Blaze vs. Shadow Knuckles vs. Rouge, Tails vs. Silver.
Sonic vs. Silver, Knuckles vs. Blaze.
Then the finals Sonic vs. Blaze. Then Sonic fights Jet.