It’s my understanding that “category 5” means “total destruction”, which is why this hasn’t been done in the past. However if it helps to get the point across about climate change, it would be helpful for marketing purposes.
That's not what the proposed change is about. (It's about replacing the scale with a different one that takes into account flooding and other dangers that better reflect the likelihood of fatalities than just wind speed alone. Category 1 hurricanes can sometimes be more dangerous than higher-category hurricanes under the current scale.) I worry that people might not take this seriously because they assume this is a frivolous rebranding to "market" climate change.