Well, it wouldnt get smaller, it would stay the same, with the other guys getting larger.
Also, id like to see the energy overtake the other person, not explode in a PS (exclusive to a PS). What i mean is how gohan killed cell without the beam exploding(episode 176- saving the world), vegeta's final flash overtaking Cell (cell saga episode UNKNOWN).
As for the ki blasts, i think they should turn into larger beams with power of ssj and ssj2. This, im reffering to Vegeta trying to kill cell for killing his son while gohan was ssj2 (episode 174- Cell Returns). You should be able to enter a "max output" kind of stage and waste all of your energy in ki blasts only. You would have limited mobility, but could pump all of your ki into your blasts and kill someone stronger than you easily. You could only do this with power of SSJ+ and other characters first transformations. Cons of this attack: Power regenerates slowly because of output drains stamina of character. Character takes a minute to recover.
Just an energy idea, ki blasts should make a lot of dust while firing in max mode, concealing the character, but the person targeted would have to block or something to avoid it, they just cant escape it cuz they dont want to fight. Kind of like force it, like make the ki blasts very inaacurate but strong, so if one hits you, you know it. Just an idea to make the game more interesting for people who like to watch other people try and kill other people. And to increase fighter stats so that the game has things you can do that have advantages and disadvantages, while keeping the game true to the anime.