I am not an expert by any means but assuming that what you replace it with is of equal or great strength you should be fine. I personally would replace with a high tech line with a padded lifeline cover. Webbing doesn't seem like it would be as comfortable.
The rule is, "14. Lifelines may be replaced with line of equal or greater strength."
The other relevant rule:
"8. LIFELINES AND STANCHIONS: Stanchions and lifelines as supplied and mounted by the builder are
required. Attachment points for lifelines must be a minimum of 11 inches above the deck. Lifelines must
be fairly taut while racing, defined as a maximum of two inches deflection from a straight line when
measured at mid-span under no load.
8.1. A forward lifeline may be fitted from the forward stanchion to the shrouds and/or a forward deck
attachment point. Whether or not a forward lifeline is fitted, when positioned in front of the forward
stanchion, crew shall not hike in such a way as to position their hips and torso any farther outboard than
they could get if the lifeline were extended, at its normal height and distance from the gunwale, forward
to the bow."
