If I remember correctly, wasn't the Plasma Torpedo just a ball of plasma. It would be impossible to provide it with mobility, wouldn't?
Now if they encased it in a tube like the photon torpedo it could be more mobile and maybe improve range and damage too. Being inclosed the plasma would not disapate over distance, but could be maintaind. Have the tube breakaway seconds before impact and bam. . .full plasma burst no matter the range.
Steven "redwood973" Wood
"Man does not fail. He gives up trying."