it maybe overwhelming. Changing a system midway don't seems fair to them. Maybe we should be looking at simplier alternatives. Having all 7 players 100% willingly agree is not easy tasks.
I think in this case, to proceed, the procedure for getting agreement should be robust. Preferably they are informed today so that they have the chance to think through. Also, in the event of one objection what is the alternative. We must respect their decision without pressuring them. All these should be made along with the reasons for the suggestion for this improvement. At all times, the professionalism, fairness and neutrality of the organiser has to be maintained.