I, personally, feel the kick starter should replace the e-starter. If you're not adding the kick starter to loose the weight of the e-starter, then you must feel your ATV needs a backup to the electric start.
Just about every electric start ATV on the planet doesn't have a kick start backup and I don't see why the YFZ450 should be regarded any differently. Just to name a few of the sport ATVs that can't have a kick starter: Warrior, Raptor, 300ex, 400ex, KXF400, LTz400.