OK, thanks for all the feedback. I haven’t played with Force powers much so I surely need the advice.
I’ve modified the original post to limit added Force die to 1/helper and added ranks to max(ranks). I also eliminated the Discipline check and simply required spending Destiny points per upgraded rank. The latter still makes it possible to do “more awesome” things with Force helpers but practically limits it.
Clean version without markup below
Assisting Force Powers
All force users must have at least the basic power being used; if they do not, they cannot assist. Alternatively, they may assist with a boost die but not a force die (GM/narrative discretion). The assisting force users must all spend a maneuver to coordinate, and commit one (1) Force Die to the check.
Force power strength/magnitude/range uses the largest rank among all those involved.
A force power rank may be extended beyond that by one rank per helper, to a maximum of the ranks in the force power tree. A Destiny point per added rank must be spent.
Each helper should roll their committed force dice during the main check. Use of Dark side pips causes strain both to the helper & primary actor if both Light side users, but only one Destiny point need be spent. If helper is user of “other side”, must contribute primary user’s Force pips to not cause them strain but helper suffers strain and pays appropriate Destiny cost.