Well 1 chaos Emerald can increase the John's own power, and speed (though for him to be able to do that he would need to know how to use it's power) while his suit if modified by a scientist or something can utilize the Emeralds power.
When John's suit is modified the suit would allow John to use the power of the Emerald to greatly increase the power of his suit. Making it far faster and stronger. If John had all 7 of the Chaos Emeralds then his suit (and maybe himself) would literally be invincible, much MUCH faster, and stronger. Though even then he would have a time limit with the super state when all 7 emeralds are obtained. As he would need rings or something else to keep the state charged (the super state will only last about 5 minutes without a steady supply of the gold rings from the Sonic games, but during that time John should have enough power to accomplish what he needs done in the mission.)
