I have a suggestion for a new division in sonic advance 3. This division would include teams that couldn't fly or tag action high jump. This would mean tails and cream could not be the leader and tails and amy could not be the partner. The reason I like this idea is because it would require new paths to be found for many levels since there are so many shortcuts involving tag action high jumps or flying.
There should also be some sort of freestyle mode where you can submit times for any team in any level. This is best left in freestyle so that way everyone doesn't have to play each level 20 times to get a good rank and allows people who like a specific team to get records.