I have been thinking. I think I can figure out how to make this work (not sure).
Character Switching
Ok. Replace Sonic character with a wad of the SPEED Formation (all 3 characters in the wad). Replace Tails character with a FLY Formation wad (all three characters). Replace Knux with a POWER Formation character. Now you will be able to switch formations by pressing 1, 2, or 3. I think that might work out all right.
SPEED Formation
The sprites for spindash can be made by making all of the characters that are put into the wad huddle close together and boost when the button is released. Super Speed Thok is the same as the regular game of course. I don't know how the tornado attack will work though.
FLY Formation
Make the formation like in Sonic Heroes where they are hanging onto one another. The wad won't be able to spindash. I don't know how the Thunder Shoot will work out though.
POWER Formation
This character can't spindash either. I don't know how to make the power character throw his/it's teammates though. Change the sprites of this wad to where when the power character glides, all charaters in the wad form the Triangle Dive.
Formation Changing Gates
The gates that you walk through to change characters. I don't know how we will be able to make them change the characters, but I have an idea for them. Make the POWER gate have a red FOF. SPEED Gate has a blue FOF. And the FLY Gate has a yellow FOF. I think that may be a cool design.
PS- Please tell me if this made any sense of not.
PSS- Just in case you did not understand, the SPEED FORMATION will be a seperate wad that replaces Sonic. The FLY FORMATION will be a seperate wad that replaces Tails. And the POWER FORMATION will be a seperate wad that replaces Knux.