Actually, adding a buff from a different ability won't affect it. The buff is just a token, really. it sits there and shows fancy effects and dictates when the effect should be removed, but it doesn't control what the effects are. So really, the only way to do this without stun is to not use Storm Bolt and instead use another ability with similar effects, or to set the stun duration to 0.01, which as mentioned will break channelling spells.