Regarding option name BSD one has --deadline option for this (timeout before ping exits) and timeout for 'time to wait for a response'. So I guess it would nice to keep the options same.
BSD doesn't use long option names, it uses -w and -W[1]. We can use --timeout=N and --timeout-response=N for the long options, since that is exactly what they do. Same goes for the variable names. [1]: You are confusing what the option argument is called in the man page, `-w deadline' and `-W timeout', it has nothing to do with the name of the option name. So it doesn't matter, and we should pick more descriptive names anyway...
