I feel this idea is good. Like games that can have two characters in one fight like mortal kombat but in head soccer. My idea is an option in Head Cup (costing 10,000 to 15,000, your choice) before starting saying on the screen "Single" and "Tag Team" and options before starting the actual tournament and you can choose two characters (able to glitch one but the other you must own) might have to make smaller because of limited characters or you could keep adding characters until you're able to add it into the game. You are only able to do this in 4 modes, Head Cup, League, Arcade, and Tournament with the same screen I explained earlier on in the idea.
Arcade
What I've been thinking is adding another token (Win without using kick,dash,etc.) saying "Tag Team Winner) but not for a sura or Pluto. You just scroll through and pick two characters (no glitches) and play against CPU with two characters also.
Tournament
Same idea as arcade but in a Tournament. Same idea with Head Cup winning idea too.
League
Once again the same but in a league. Also same with Head Cup winning idea.
Head Cup
May not have enough characters for how large this is but choose two characters and win the same as a normal head cup and get same amount of points. However if won same with normal, you get a crown little bit different than the crown in normal saying Tag on top and Team on bottom, place somewhere on head so able to see when scrolling through characters.
Gameplay
Option by controls that say Switch or Tag, in which a laser comes quickly .5 second delay of character switch (do best for no lag or crash) time for each match is 1:30. 5 seconds to switch character delay after already switched. Power ups for each character would work perfectly. Any type of duo would work (even overpowered ones)
Thanks! If added please have honorable mention to Trey.