Sorry for my bad english, do not hesitate to correct me.
Third strike rom are impossible to edit if you’re not a pro rom hacker and even if you are, you’ll need a good amount of time. Cps3 rom are all encrypted by Capcom.
In order to edit the rom itself, you must first break the csp3 first, and believe me, that’s not easy task at all.
After you done that, you’ll need to understand the encrypted language in the rom. This part’s not that difficult, once you’ve entered the rom game’s files, and find a way to alter them.
Plus, you’ll need a very good graphist/animator in order to add shit to the game, because you’ll need to draw sprite before implementing new thing to the game ( like Akuma new SA, or Chun new wall bounce move ). You’ll have to emulate third strike’s style.
You can’t see all the game for the video you posted but let me tell you that you can’t really add something to the game. All you can do is edit stuff already present in the game. For exemple, i’m pretty sure that Akuma new SA replace some Akuma’s old SA. In order to add something completely new to the game without editing something else in the game, you’ll need to expend the size of the rom. This is possible, but this is an uphill task.
However, supress or alter some minor thing in the game is not so difficult. For exemple, if you want to supress character or move in the game. If you want to supress fireball, necro, oro, yang or make Urien C.hp two frame faster. Thing like this are not easy shit but are very doable once you’ve understand the source code’s language.