There are differnet types of ping usable in netwatch.
The simple is "simple" 
.
There is ICMP that - properly configured [1] - has more features, and probably could do what you need.
Otherwise you could have as "down" script, a script that itself pings a few times and only if it fails resets the usb power, that can be also assembled in more "stages", loosely like : Advanced NetWatch
[1] much easier to saying that than actually doing it