As written, a darksider imposes his will more strongly with the battle meditation power, reflected in the rules as a penalty to willpower. However, I dont see a corrosponding benifit.
The MAstery upgrade implies it is usable on people who would resist- but as written, it can only affect friendly characters.
Perhaps the darkside version can expand to unwilling puppets? So it can target any friend or foe, and impose a Advantage or Complication with each force point, and drains Willpower if you use the Dark side... perhaps draining more Willpower with more darkside pips?
Suggested changes:
Basic Power: Remove the word "Friendly" from "Engaged friendly targets"
Add "If the force user spent any Drkside on this check, reduce the targets willpower by 1 (to a miimum of 1), and you may choose to inflict Complications instead of Advntage "
Mastery: Add to "If the user spent darkside..." "The user may spend 2 Forcepoints per setback they wish to add to this check."