Rain has been a bigger issue than wind.
When you look at how hurricanes get their rating, the wind speed has always been the key factor in describing the strength of a storm. It is wind that is also the principal drive of storm surge, that is the ocean coming ashore, being driven by the wind.
In the past few years, rainfall has been as dangerous as the wind with massive amounts of water being dumped on land. This has caused flooding in places that have never experienced flooding before, e.g., Hurricane Harvey.
Now Tropical Storm Barry, at this writing over the weekend, is about to provide significant amounts of rain. More rain than what the city of New Orleans' pumps can likely handle.
If they do move forward with establishing a category for rain along with wind, perhaps the best thing to do is not use a number, but a letter. Keep the 1-4 for wind speed and then add a "letter grade" for rainfall predictions. Figuring out where it will rain or when the storm will stall over a geographic area will be the challenge.
Likely it will take forever before any change like this is made. Science and government move slowly, especially when there is a long history and an established system already in place.