as one who designs this type of stuff for a living, you would gain nothing from switching to HMWPE over traditional nylon. There are some other fibers int he works that behave better in hazmat environments, but from a price/performance perspective you can't really beat the nylon that's being used today. Keep in mind that while it does degrade in water, especially quickly in salt as it will absorb salt and abrade against itself, the stock breaking strength is somewhere around 4000 to 5000lbs, even if it loses 80% of its strength, it will still hold up 800lbs, and it takes an awfully long time for it to break down to that point.
HMWPE 2" webbing is commercially available, but it is only used in very specific applications where weight is a concern, otherwise nylon is still king, and you really don't want to know how much it costs.... Easily an order of magnitude more expensive than nylon