DCC (chat or send) through a IP-NAT on an Amiga is possible, just a pain to set up at first. AmIRC doesn't know about IP-NAT so you'll have to use TIADCC (perhaps along with a dyndns account) or a script to set your Amiga's internet hostname (which is the big problem, not the firewall). Then redirect a few high ports to your Amiga (say 1050-1055) and dcc should work - after some trial and error.
