FTP Client Proxy Restrictions

[tacochowder13]

I'm using FTP Client Proxy, but I'm wondering how I can limit which hosts have access to use it.  Currently you can exclude, but not include.  If you exclude, the rules end up looking like this:

no rdr on ix1 inet proto tcp from $workers to any port 21
rdr pass on ix1 inet proto tcp from any to any port 21 -> 127.0.0.1 port 8021

I need to restrict my entire DC except a few hosts from being able to FTP, so I'd have to maintain an alias with everything that's not allowed?  That seems backwards.  Why can't the rule be more like:

rdr pass on ix1 inet proto tcp from $permitted_ftp_hosts to any port 21 -> 127.0.0.1 port 8021

Or maybe the ability to enter my own custom entry so I could do something like:

rdr pass on ix1 inet proto tcp from { $ftp_clients $user_laptops } to any port 21 -> 127.0.0.1 port 8021

Thoughts?