It has already been several times discussed how it is status-bydesign that Area 51 reputation is not taken into account for the commitment score
But it would perhaps make sense to include in the formula (if it is not already, I was not exactly sure) the number of fulfilled commitments as recorded in Area 51. I believe including this would give a good idea of the number of committers likely to fulfill their commitment for this particular proposal.
However, I do not find this essential, just a refinement of the existing system. And I expect other people might find that it is already accounted for by the reputation they will have gained by participating actively in the previous proposal.