I was thinking the same thing... the spirit bomb is almost useless unless your near an object so it can explode near someone. In the air it's just too easy to avoid.
Something i was thinking about... Enable a 2nd Function for the Spirit Bomb, It would make a smaller, faster moving and charging, and more accurate spirit bomb, the downfall.. is it's a lot weaker, and the explosion radius is smaller.
Basically what i think it would look like, is the small aura around the hand fireball, exactly like in the Saiyan Saga, used against Vegeta..
Sound good?