New hacker starting tag team mod, need help

[aD_Time]

I'm looking to make a mod where you choose 2 characters and make it so you can swap out between them mid game. I think there's already a mod built into 20XX for this but I also wanted to add in the ability for the second character to come in and assist by pressing a direction on the D-Pad. They would spawn in where the main character is and do their attack then leave the stage. I have absolutely no idea where to get started on making this and would appreciate any help. Thanks

 

[LudwigTweets]

Were you thinking of something like this?