seems odd, give one of these momentum and it essentially gives all creatures momentum. i know you could say "but pc skills/abilities/spells can destroy shields, too", but then you have to take into account that this affects immaterial shields and the effect will be reapplied to new shields (ie if phase shield is played, nullified, and then played again, it will again be nullified, and so on and so forth.
and why did you choose light?