I think he means the ability to firewall ranges like this:
192.168.1.1 through 192.168.1.100, inclusive
Would only block 100 ips, but 192.168.1.101 could connect. There might be a few tricks you could do as far as using several filters to get the same effect, but my guess is this is what he meant by range.
As far as adding it goes, not positive it's a coremod (check the scripts/accounting folder, theres firewall and iplimiter files in there), but i'd still like to see it. Not gunna hurt if they aren't put in though, I've been blocking ip ranges at the router if needbe. Thankfully, only had to block one guy that way so far (kindof a pain to set it up, but then again they're blocked from the network, not just uo
)